Fair enough, some folks don't want or have a need for 5.1, so that's their choice ultimately.
2.1's sound fine.
I wouldn't do the heatsink you chose however. I used to be a big fan of AS Freezer products, and they're still great heatsinks, but you can do better for less.
Namely: Newegg.com - COOLER MASTER Hyper 212 Plus RR-B10-212P-G1 "Heatpipe Direct Contact" Long Life Sleeve 120mm CPU Cooler Compatible Intel Core i5 & Intel Core i7
I have that heatsink and it keeps my 1100T downright chilly. Even at full load rendering video, the most the CPU does is 42*C. (Proof
Also, for that monitor, CrossFire would be an added expense without a real gain. To see a great improvement on high end cards in CrossFire/SLI, you should have a monitor with a resolution capable of higher than what the 24" one you chose can do. One card will be plenty with this setup.