What kind of pdp ram are you using currently? Honestly, you probably won't get much more than a 2-4% performance improvement by going with other ram. You're probably better off just using memory dividers get a better cpu oc.
You won't notice any difference between 2 gig's of ram unless you are a power-user, using photoshop or playing bf2. Also, you will get hit with the 2T penalty by using 4 dimms. If you are going to go with 2 gigs, get 2 x 1gb sticks.