I have no trouble with mine. It's currently idling at 36 degrees C, and behaves admirably in intensive stuff - Far Cry, Aces High, Toca, UT 2004 etc - when it runs happily at 51 degrees. It's a Pentium 2400 with a R9800 Pro. Given that you're avowedly not playing ganes, then you might as well go for the R9600, though even that might be overkill - would a R9200 not do?

Expandability isn't really an issue - you get one AGP slot, one PCI slot, one 5.25" bay and 2x 3.5" bays (one open, one hidden). Just about everything else (USB, LAN, sound, serial, kb, mouse etc) is onboard. Most people don't need more, but if you do - e.g. my main workstation has 4 drives in a RAID 0+1 config - then a Shuttle isn't for you. I'll echo the comments about Matrox, but I'd suggest you'd be better off spending your money on LCD monitors. Get yourself a pair of 19" ones and marvel at the amount of space you suddenly have on your desk.

It's small, it's easily transportable and you can buy a carry-case for it. I take mine to LAN gaming sessions, but equally you might take it to a client.