Are you wanting to overclock your RAM? If you are, then you want to head towards brands like Mushkin etc, but if you're not too bothered, then go for OCZ or Corsair.
Personally I think 3Gb is overkill, and 2Gb will be fine for at least another 3-4 years (assuming there is no huge leap in gaming etc). Also remember that Windows only really likes 2Gb, and tends to screw up with anything over 2Gb.
You'd also be better off going for something like Dual Channel rather than two stand alone sticks of RAM (they perform much better in Dual Channel mode).
I've got CAS latency timings of 2-2-2-5 on my OCZ 2Gb (2 x 1Gb) Dual Channel Platinum Series DDR400 which is OK I think?? I'm not too good on timings, but I think the lower the numbers the better
If you can, avoid value RAM, it's not worth the money. I'd advise you to get either OCZ, Corsair or Geil if your not overclocking, but get Mushkin or G Skill if you are deciding to.
Hope any of this helps!
EDIT: I've seen my friend overclock his RAM, and it didn't really speed up his system, and all I could see it do was up his benchmark scores which aren't important at all. But it's up to you.