IMO Media Center Edition 2005 is leading the way in PVR software. Meedio is much more customizable, but that also relates to much more fiddling to get it right. Last I checked, Meedio did not have PVR capability in it's offerings, many Meedio users use Meedio as the front-end and SageTV as the PVR software. Media Portal is an interesting freeware port of the XBMC project to the PC platform.
XPMCE2005 is the only polished solution which does both SDTV and HDTV/DTV recording. However, HDTV is OTA only, no way to record/playback HDTV from your set-top box or DTV receiver. But, I expect that this is in the works, likely held up by DRM concerns from the content providers. BTW, what will be needed for the USA is a PC based HDTV capture device/tuner with a cable card slot. This hw is currently non-existant.
In my opinion, the HTPC will really be interesting when it has full satellite/terestial/OTA HDTV PVR capability. Imagine a remote-controlled HTPC with a slick front-end that gives you an interactive TV program guide, capability to record & playback HD and SD TV, a searchable DVD jukebox complete with trailers, cover art & preview/trailers, FM stereo, including recording, searchable mp3 jukebox with artist info, covers. etc., and photo slideshows. Pristine HDTV video is guaranteed via DVI output to the HDTV, audio to dedicated component home theater equipment via SPDIF w/ DD5.1 & DTS passthru.
Ok, I'm rambling. Here's some tips: I like MCE2005. MCE2005 hw requirements are the strictest of all HTPC software programs. If you register on the MS OEM System Builder website, you will gain access to a Powerpoint file which outlines how to construct a MCE PC as well as hw requirements for MCE2005. By the way, regardless of which software you go with, avoid software encoding PVR cards. By staying with MPEG2 hw encoding TV-tuner/PVR cards such as the Hauppauge PVR-250, your CPU requirements are greatly reduced. IIRC, for MCE2k5 w/ MPEG2 sw encoding min equiv CPU speed is 3GHz. For hw encoding, min eqiv CPU speed is reduced to 1.6GHz. Thus if you stay w/ hw encoding tuners, a low-power XP-M or undervolted P4 2.4C Northwood will be plenty of horsepower and can be cooled very quietly. The Pentium-M will be an awesome HTPC processor with it's fine performance and extremely low power consumption, but is priced out of reach for most of us. It also has an achilles heel in it's less than stellar video encoding capability.
For video cards, you probably want to stay with a passive card. The recommended video card list for MCE 2005 is at http://oem.microsoft.com/downloads/MCER ... r_MOSB.xls
. I use a Radeon 9600-128, but there are other good choices both with NVIDIA and ATI chipsets. If you're a gamer, Gigabyte has a passively cooled GF6800 card.
Note that you will need both a PVR/tuner card and video card. If you intend to output to a HDTV display, I suggest using a display and vid card w/ DVI. Ideally, your vid card will natively support your display's HDTV resolution.
In regards to motherboards, features to look for are undervolting capability, on-board sound with SPDIF outut w/ DD5.1 DTS passthru and other silent computing features such as pwm controllable fan headers, cool n quiet, etc. Check out Aopen's offerings.
By the way MCE2005 has a significant achiles heel in that it records TV in a DVR-MS file format that is not playable on standalone DVD players. It is directly convertable to MPEG2, but the conversion process can be problematic and requires 3rd party sw. SageTV & BeyondTV record in MPEG2. BeyondTV also has other option including wma and Divx.
Hope this helps.