X2 3600+ oc help

[Maverick986]

just built a new computer for my brother and looking to oc it....i was wondering if anyone here has oc'd a system sinilar to the one i just built or has any idea of a good ballpark as to how much i can oc it.....i'd like to just sit there and play with it all day and w/e but i really don't have the time right now and was hoping for some idea how much it can be pushed.....

system:

ASUS M2N-E Socket AM2 NVIDIA nForce 570 Ultra
AMD Athlon 64 X2 3600+ Windsor
G.SKILL 1GB DDR2 800 (PC2 6400) and G.SKILL 2GB DDR2 800 (PC2 6400) both run at 5-5-5-15
Thermaltake Ruby Orb

right now at stock the cpu temp is sitting at 20-22c...