Adding RAM - CAS Latency and Timing

[ForestHIllsRob]

I want to add a 2 GB set of RAM.

My specs are:
Windows XP SP3 P4 3.0GHZ ASUS PTGD1-LA Motherboard.

I currently have two 1 GB sticks of RAM - PNY and KByte. Both show a timing of 3-3-3-8, and neither has a heat spreader.

Questions:

1) Must I buy more RAM with the same 3-3-3-8 timing?

2) If no, is RAM with a timing of 3-4-4-8 compatible with the RAM I have now?

Thanks,

Robert