One option is the dual-tuner $299 TivoHD, which can be had for $260-$270 from Best Buy and Circuit City.
Note the current TivoHD software has issues with Scientific Atlanta CableCards, so at least for now, I would only recommend that product if your Comcast uses Motorola CableCards. If your Comcast DVR is made by Motorola, then they have Motorola CableCards.
The TivoHD will simultaneously record any two digital SD or HD channels at 100% original quality while you watch a third, previous recording. There are no consumer products with the ability to record three channels at once, but the Tivo is far more 'intelligent' in how it records, so you can record more shows with less effort. For example, if three of your favorite programs are all showing at the same time, the Tivo will record two and then automatically schedule a recording for the next airing of the third program without any user intervention.
The TivoHD has a 160Gb internal drive -- the same size as the Motorola DVR. Unlike the Motorola DVR, you can easily upgrade the internal drive to 500Gb, 750Gb, or 1Tb. The TivoHD also has an eSATA connection; Tivo told reviewers will support storage expansion via eSATA later this year.
Some advantages of the TivoHD over the Comcast DVR:
- Want to remove channels from your guide? Tivo lets you do that.
- Want to expand DVR capacity? The Tivo's internal drive is upgradeable to 1Tb (131 hours HD, 1244 hours SD), and official support for eSATA drive expansion is coming later this year.
- Tired of remote lag (and remote 'queuing up') when using DVR functions like instant replay, fast forward, rewind, and 30s skip? No such lag on the Tivo. DVR functions are instantaneous.
- Series recordings are neatly organized into folders. Have four episodes of Heroes on your DVR? They're all grouped in a single folder called "Heroes." Within the folder, the recordings are listed by date with the actual episode title. If for some reason, you don't want folders, you can disable them. Screenshot here.
- Want buffering on both tuners, so you can switch between two different channels and rewind, or pause one channel, switch to another, and then switch back and resume where you left off? Tivo does that.
- Tivo has a "wishlist" feature that will automatically record content based on keyword, genre, actor, director, or virtually any other criteria you can think up...regardless of date, time, and channel...and neatly organize it into folders. This is possible because Tivo offers far more meta data (i.e. program information) than cable providers. Examples:
- Like to watch westerns, but only want them in HD? You can create a wishlist to automatically record all westerns broadcast in HD -- regardless of date, time, and channel -- and the Tivo will group them all in a "Westerns / HD" folder, with the contents listed by recording date with the title.
- Only want westerns directed by Clint Eastwood? You can set it the Tivo to record all westerns directed by Clint Eastwood that are broadcast in HD and it will group those in their own "Westerns / Clint Eastwood / HD" folder.
- Obsessed with Paris Hilton? You can set the Tivo to record every Paris Hilton interview shown on TV, regardless of date, time, and channel, and all will be neatly organized into a "Paris Hilton Interviews" folder.
- Looking for a specific episode of Seinfeld (or any other show)? You can create a wishlist to record that.
- Looking for an old episode of Oprah with a certain guest? You can create a wishlist to record that.
- Interested in World War II weaponry? You can create a wishlist to record all programs about that topic, regardless of date, time, and channel, with all neatly grouped into a folder.
- Just want to find a program? Tivo makes it simple to search the next 14 days of listings. When searching by title, the results update dynamically as you type in each letter using the on-screen keyboard.
- Want to receive OTA channels? The Tivo will combine analog and digital broadcasts from both cable and OTA into the same guide. As before, you pick and choose what channels you want to show up in the guide.
- Want to avoid re-recordings of episodes you've already seen? The Tivo keeps a record of the last 28 days of recordings and deletions, so it knows not to record episodes that you've already watched and deleted.
- Tired of missing new episodes because your cable provider improperly flagged new episodes as repeats? Tivo actually makes the effort to get their guide information right. It's not always perfect, but no one offers higher reliability. If there is a last minute programming change to one of the programs you've set to record, they send a message to your box.
- Did your cable company remove the 30sec skip function? The Tivo remote has a button for that.
- Want an "all native" output mode to output 480i channels as 480i, 720p channels as 720p, and 1080i as 1080i without lossy conversion from one format to another? Tivo has that.
- Want built-in pillarbox, stretch, zoom modes for SD channels with the ability to change between them by pressing a button on the remote? Tivo has that.
- Want to extend recordings in progress, such as sports that are running over? Tivo makes it easy and fast.
- Want to schedule recordings over the web or from your cell phone? Tivo does that.
- Have three programs you want to record, all showing at the same time, but only have two tuners? The Tivo records the two programs you've defined with the highest priority, and then automatically schedules a recording for the next available showing of the program you missed. You don't have to do anything to schedule a recording for the third program.
- Tired of missing a 9pm recording because some network ran their 8pm program a few minutes over? Tivo eliminates that with overlap protection.
- Want to listen to Podcasts on your DVR? Tivo does that.
- Want Internet videocasts like CrankyGeeks, DLTV, The Onion, Cnet, and Rocketboom to automatically show up on your list of recorded programs every week just like television shows? The Tivo does that.
- Want to purchase movies -- streamed direct to your DVR -- from Amazon Unbox without a PC? Tivo does that.
- Want to view pictures stored on your PC on your DVR? Tivo lets you do that.
- Want to listen to music stored on your PC with your DVR? Tivo lets you do that.
- Have a Rhapsody music subscription and want to access all your Rhapsody songs, playlists, and channels without a computer? That feature is coming to the Tivo with an update later this summer.
- Want to stream high-def recordings from the Tivo in your living room to the Tivo in your bedroom? Tivo has said an update to enable that feature is coming later this year.
- Want to copy high-def recordings (on channels flagged 'copy freely') from the Tivo to your PC using a wired or wireless network? Tivo has also said the update to enable that feature is coming later this year.