20 years ago I played with the idea of using separate amps for woofers and tweeters and then using a PC with multiple audio outputs as the crossover. Unfortunately back then the PCs had too little power so I dropped it.

Now in 2008 I'm building a new home theater and went googling for information, but with limited success. The idea: a 7.1 setup with decoding, room correction and X-over in the form of DirectShow filters all done in software. No coils and capacitors to worry about, just 2 or 3 times as many amplifiers.

First question: Since processing 8 channels of audio would consume a chunk of processing power I was thinking maybe there exists a filter that will send the audio stream across ethernet to a second PC which would handle all the audio?

Second question: If one installed 2 or more sound adapters, would it be (im)possible to route the different "parts" of the signal to different outputs in directshow after going through a crossover filter? Maybe Directshow isn't suited at all?

Third question: I can't seem to find any multichannel capable crossover filters?

For 7.1 that is 15 output min out of the PC. You are way out of commodity space. This would be a very special setup you are thinking about. I don't think Directshow is setup to do this sort of thing.

Be sure to consider HDMI and High Def audio. Even 7.1 channels of uncompressed audio is a not something that "just works" on your PC.

Another option might be to stay active using commercal pro audio crossovers. Off load the work to something else that is build to be a crossover. I would look into the pro-audio world maybe that have some PC tie in technology.

Have Fun.

The single cheapest PC you can buy can do cross-over for 8 channels without breaking a sweat. Remember: PCs these days are used as virtual synthesizers, multi-track recorders, samplers, and effects processors. An entire recording studio in a $1,500 box.

For the inputs/outputs you need, you need a "studio" sound interface; something like the Echo Layla, ProSonus FireStudio, or M-audio Delta 1010.

However, there likely exist boxes that do what you want to do, without the PC. These days, putting a DSP and some I/O into a 19" rack unit is pretty simple. If you go with a cheap PC based on low-power parts, you can probably get away without active cooling, but it's still more work than I think it'll be worth to roll your own.