Hey bob - Check out the Kingston website, you can select your motherboard and it will tell you which RAM is compatible with it.
http://www.kingston.com/hyperx/default.aspWhen it comes to latency timings (e.g. CL 2.5-3-3-5) the lower the numbers the faster the RAM. They are measurements of how many clock cycles are needed to achieve certain things such as time to first read.
ECC vs Non-ECC: ECC is RAM with inbuilt error detection and correction (error-correction code = ecc). Most motherboards do not support this type of RAM. You would normally find ECC RAM in servers, not desktops.
If your mobo supports both, I'd go for Non-ECC myself as it is faster, easier to overclock and cheaper.
I've been looking into RAM upgrades recently too. Definately recommend Kingston Hyper-X, seems to have the edge on Corsair atm.