I can see 3 main directions when talking about HTPC/mediacenter:
1. Audio/videophile that wants the best May have projector or plasma screen og a high quality audio system. Wants a large box with premium parts. Is willing to spend time tweaking ffdshow, perhaps roomcorrection, maybe builtin touchscreen or home automation system.
*Intel Core 2 Extreme or Athlon 64 FX-62, possibly 2x dualcore
*last generation nvidia/ati GPU
*plenty of ram
*lydkort w/ spdif ,surroundamp
2. Regular user with crt-tv or lcd-tv. Wants good DVD playback, some HD, interested in live tv showshifting/recording. Wants bang for the buck
*intel core2 6300/6600
*Nvidia 7300/7600
*512-1024MB ram
*1-2 tvtuners
3. Media-center. Primarily using the computer as a juke-box (lazy). Maybe audio-only or possibly some DIVX/DVD. Can usually get by using very moderate hardware and wants a small, cheap and noiseless box. May consider a remote, hidden fileserver for larger media-storage.
*VIA mini itx or Core2 eller AMD (mobile versions)
*512MB ram
*lowcost GPU or integrated ala nvidia 6150
*either spdif/surround-amp combo or analog 5.1 capable soundcard with speakersystem
3b. Mediacenter with lots of storage. Same as above but with a larger enclosure to allow 3TB of storage
*a large number of Samsung or other lownoise disks of ~500GB each
I am shure there are lots of users that disagree on my partition of users, but it was an attempt to collect some broad groups with similar hw/sw needs. The total cost, ergonomy, noise and size is highly dependant on what group you find your self in.
regards
Knut