Either one would be fine.
Before I tore all my PC's apart, this is what I used for Mythtv:
Mythtv Backend/Desktop/Gaming machine:
Debian Linux (Sid)
120gig and 80gig WD 8meg "special editions"
1gig ram, 400mhz (ddr, underclocked for a 133mhz buss.)
2400+ AMD.
ATI Wonder VE
WinPVR-250 (hardware mpeg2 + tv tuner)
(with 2 encoder cards I could do stuff like PIP stuff, and record shows while I watched on a different channel. Mythtv supports multiple front ends and multiple back ends with multiple video cards. MCE, I beleive, only supports one or maybe 2 cards)
For my front-end I used:
Fedora Core2
256megs sdram
4gig harddrive
800mhz celeron
With a nvidia Geforce 420MX with Tv-out
You should buy a Win
PVR-250 or
350. These guys are the premier PVR for regular SD (normal TV resolutions)PVR stuff.
Now the next most important thing besides the tv card/mpeg2 encoder is the harddrive. This is how a PVR time-shifter works:
cable ---> tuner ---> mpeg2 hardware encoder ---> media file on harddrive ---> program plays mpeg2 file ---> decode mpeg2 ---> display and you control playback and have fastforward, pause, and rewind just like on any other media player.
So for high quality your going to be writing to the harddrive and reading back from the harddrive at the same time. This takes a fairly fast harddrive.
Also harddrive capacity is important. A 1 hour show in high quality mpeg2 format can take a few gigs. The same thing encoded into mpeg4 compressed format will take up maybe half to a third depending on quality.
I suggest getting a big 200 or 250 gig harddrive at 7200rpm and 8meg cache. Should be fast enough and big enough to store quite a bit of shows. If you have the money, and if MCE allows it, you can get a fast 10,000rpm harddrive for active use and use the a larger slower harddrive for longer term storage. That will improve seek time and such. (mpeg2 files generally have crappy seeking ability vs other uncompressed video file formats.)
Then after that the cpu doesn't matter so much, nor does the memory (although that stuff helps). The hardware encoder on the tv card takes the brunt of load off of the cpu. And decoding mpeg2/4 doesn't take nearly as much power as encoding it. My 800mhz celeron handled decoding mpeg2 just fine.
For some terms:
mpeg2 = this is a standard digital video media broadcast and display format. This is what dvd movies are encoded in, this is what digital television is encoded in. This is what digital satillite is encoded in.
Note that HDTV ISN'T the same as digital media. HDTV can be analog or digital.
Mpeg4 = this is a standard high-compression file format. This is what .avi files are typically encoded in. Divx is a popular mpeg4 encoder, Xvid is a open source alternative. I prefer to use mpeg4 encoder from libavcodec, which is superior in speed and quality and file sizes to Xvid and Dvix.
mpeg2 hardware encoder = uses circuitry to encode mpeg2 media with very little cpu usage.
Unfortunatly MCE only can use hardware encoding cards, with the exception of maybe ATI ALL-in-Wonder cards with a add-on package that will do the encoding in software.
Otherwise those machines you outlined will be great. Plenty fast and shouldn't have any quality issues with anything.
