Just curious? What do you dislike about MCE what you don't want to use it? The integration is so freaking tight between the MCE and the Extender in the 360 that everything works great. The only real downside is that you can't play all formats of video in the Media Center/Extender scenario.
We use this exclusively at home and it works great.
Any reason you can't just use an HTPC for streaming? I bought a 59.00 Diamond Xtreme Dolby Digital Live card which converts all audio sources to Dolby Digital 5.1 (even the Creative Xifi cards don't have Dolby Live which is hella lame). I use TOS cable to connect to my home theater receiver for audio and then DVI from my computer directly to my Projector. It makes for some great home theater no matter what audio or video format you have.
The good news is that the Xbox 360 hacks are out but only for playing copied games. What we need is XBMC for the 360. Maybe soon: