For a starting point. try their list
Though in general, RAM is RAM.
If you want a total of 8GB, best to use an 8GB dual channel kit (2x 4GB) though sometimes it can be cheaper to buy as two 4GB - the kit won't be any better than "two of the same".
Looks like the top-end CPU's for that support 1866 (non-overclocked) - actually, that seems to be standard for the AM3+ CPUs, compared to the AM3 CPUs where it was 1333.
You can run RAM slower than maximum, so even if you have a AM3 style CPU at the moment, I'd suggest DDR3-1866 so it would have full speed for an AM3+