Fastest LGA 771 Xeon

hey guys

so i have a thing for old hardware and so my lan pc currently runs a gtx 480 watercooled with a q6600 2.9ghz.
id like to use the 2nd identical 480 ive got (same aquagrafx480 block) and run them together because why the hell not i like the look of it. now i have the opportunity to get an Asus striker 2 ROG board for cheap and i really want it so i'm thinking of pairing that with some form of lga 771 xeon because current Q6600 is admittedly bottle necking 1 480 but screw the price of the high end C2Q's. this projects gonna be slooooow to finish because i have to buy a big ass power supply *fun* with my small amount of cash but for me it will be totally worth it even though i have an already much better pc (although with how much trouble its been giving me i might end up parting it out to fund this sli 480 rig xD)

so anyway i found an E5504 for $10 (AUD) $10 and i also found an x5650 for a little more so does anyone know which is the better cpu and also if someone could give a list of the best xeons for the job so i can hunt the used market for them as well that would be fantastic.

like i said before this pc is just thing i want to do i actually enjoy gaming on the single 480 q6600 pc more than i do my main far better pc idk why maybe just because its nice to see old hardware play games it said not to be able to but im rambling so yeah best lga 771 xeons give us a shout guys.
Cheers