The more memory you have the looser the Ram timings would be. The main thing that you probably heard about is either when you no longer run in dual channel or if you run in 2T instead of 1T.
Basically you want to have 2Gb of ram (2x1gb) or if you really want 4Gb then go with (2x2gb) but that doesn't seem needed for this build and would mess up your budget. I think the ram you already picked is fine.
One thing I would suggest is perhaps get this Power Supply instead:
OCZ GameXStream 700W Power Supply - $159.99 but down to $134.99 after $25 mail-in rebate.
It is a really good quality power supply, I personally have it and it runs my 8800GTX perfectly along with everything else.
I would also grab a 160gig or 250gig HD for him. I use a small one but that is because I like the 10,000 rpm and am too cheap to get a big one of those. A lot of people like to have large HD's to store a bunch of stuff.
Here is a cheap one that is decent: $62.99
or if you can get him to fork up the cash this one would be REALLY nice to have, 10,000rpm makes a really nice difference: $219.99 but only $189.99 after rebate