My thought on the matter would be to overclock your present XP, and save your money until you have enough/and prices drop enough, to make a big jump, to say an XP2700.
I have my Xp1600 running at XP2200 speed right now, at 1.775 vcore. It may be a better overclocker than your chip, but I really think that you can do much better for your money if you hold out a while longer.