Already read the UPS FAQ, and I need some more advice.

I just read the UPS FAQ carefully, and while it is very informative (kudos to Somejoe7777), it doesn't tell me exactly WHAT I need for my needs. So I'm hoping the experts can give me some specifc suggestions. Here's the rig that I'm running:

CPU: Intel Core 2 Duo 8400
Mobo: Gigabyte DS3R L775 P35 w/ 2GB DDR3 mem
Grfx: MSI Geforce 8800 GT 512 MB OC
Hrd Drvs: 2x Western Digital 250 GB 7200 RPM
Snd: Sound Blaster Audigy EX
PSU: Antec 400 Watts

I think that's all the relevent (too much in fact!). My questions are, should I get a UPS that's better than stand-by/square wave quality? And what kind of VA rated UPS will I need? Any advice or suggestions would be greatly appreciated!