I like the user interfaces (menus, control options) of the Zenith and Digital Stream better than that of the ChannelMaster. But that sort of thing is partly a matter of personal taste.
Yes, the CM's font is definitely the least desirable of the three (and would be pretty darned small on a 24" set), and the menus are extremely plain, but he just said he was mainly looking for better PQ.
It might not be better than the DS's, but the guide on the CM is definitely more comprehensive than the Zenith's.
Thanks for the comments on the 9950 vs. the zenith or CM7000. I'm surprised I get any reception at all since I'm in a basement apt in a city using an indoor antenna, but I can get all but a couple channels to come in at 80 or higher strength if I fiddle with the antenna a little. I've been pleased with DTV. I have one more coupon to use, I'm trying to see if I can get either a zenith from sears or a CM7000 somewhere using my coupon since my Sony KV24FS120 TV does have S video. Are these boxes generally considered to have better tuners than most built in tuners on HDTV's?
At some point, the built-in tuners on HDTVs will catch up. They may already have for some models/mfg dates. But, at least as of last year, CECB tuners generally were more recent designs than those in TVs.
You sound like a candidate for using a YouTube coat hanger homemade UHF antenna One of those hung from the ceiling (near a window, if possible), might improve reception. Not so good for actual VHF stations, though.
I have two televisions with built-in ASTC tuners: a Vizio, purchased Dec 2008, and a Toshiba, purchased Apr 2009. The tuner in the Vizio seems fairly poor, but the total lack of a signal meter and other conveniences might be clouding my judgment ... my opinion might be unfairly harsh. However the tuner in the Toshiba is excellent; it also has a nice signal meter. It is at least as capable as my Zenith DTT901 and Tivax CECBs.