Even if it needs more RAM, you can pick up 2 X 2GB for around $100. If you already have 2 X 1GB in 1 & 3 or 2 & 4 of the DIMMs, you are still better off using 2 X 2GBs. You have to be careful with RAM. A mother board can only support so much RAM and sometimes you can have unequal DIMMs and sometimes not.
One thing some people don't know, which I found out the hard way is that if you are using a 32 bit OS, which most people are, the OS can only "see" from 3.2 to 3.5 GBs of RAM. With my server, I went ahead and did the 4GBs, because I needed as much RAM as possible and got lucky that it can see about 3.4GBs
