Sub-$300 with Dual-DVI and lots of memory (4GB if possible.)
Don't need a lot of storage, but gigabit ethernet + wireless would be nice.
Needs to be quiet as well---3.5 db or thereabouts.
DDR2 vs DDR3
Back in 2007, it appears DDR3 was more expensive without any benefit. http://www.tomshardware.com/forum/245145-30-ddr2-ddr3
Today, 2010, 2GB of DDR2 PC6400 is about $50. DDR3 is only about $5 more expensive but claims much faster speeds.
AMD vs. Intel
I have always liked AMD. Nowadays, AMD seems to have a much better price point.
The socket AM3 set seems to provide the best price/performance ratio.
Apparently, you can unlock 2 more cores on the above to get a quad-core system. It's only 65W, which is very low. Low watts means low power means less fan noise.
Motherboard integrated graphics is a must. I might upgrade later, but it's unlikely.
Case and Power Supply
Lookign for something quiet.