Best upgrade path for little LAN box

[tigerstyle]

I've been given the following rig from a friend to get back in the LAN scene after years away from it. So obviously it's not a mega 1337 rig but it's better than nothing, wondering my best way of spending the minimum $$$ to get it fairly decent.

Q6600 - Stock HSF and only in a small mATX case so not room for a bigger cooler or overclocking I don't think.

Asus P5K-VM mATX mobo

OCZ 600Watt PSU (ozx600sxs) shouldn't limit me GPU wise?

3Gig Ram 3x1Gb, might want more in there?

500gig HDD

AMD 5450 GPU - the deal breaker!

I know the GPU has to go, but it's only in there as a temporary measure, I don't think I'm limited GPU/PSU wise, it's just about finding something new/second hand that will not be wasted or overshadow the rest of the system.

Luckily the games are pretty easy going, ARMA2, L4Dead2, Chivalry, TrackMania2, BF3 maybe.

What's the recommendation, I'll be going for a 24" 1080P display most likely.

 

[tigerstyle]

Cool, had one of those in a 'maybe' build a year or so ago, nothing will be heavily bottlenecking that?

Would moving to 2x2 or 1x4 stick of newer ram help? Should be cheap if found second hand? 3x1 sticks seems a bit thrown together to be as efficient as it could be maybe?

 

[tigerstyle]

DDR2 is kinda hard to track down, to the MM it is!