1.36b or 1.8 are good to start with.. 1.9b5 is somewhat untested yet and has bugs.

2.5-3-3-6-13-15 might be a good place to start, then you can drop TRCD and TRP from within windows while running prime95 or super-pi.. trc and trfc might not like going under 13-15 depending on the chips they use.