Hi there

I'm currently running a 6850 and a 5850 on a 600W Corsair PSU in:

Corsair 600W CX Builder Series 80 Plus PSU
Core i7 2600k
Corsair Vengeance 8GB (2x4GB) DDR3 1600Mhz
Gigabyte GA-Z68X-UD3-B3 Z68 Socket 1155
Arctic Cooling Freezer 7 Pro rev 2 Socket 1155
1 SSD
1 HD (7200)
3 120 MM fans
1 140 MM Fan
1 DVD RW

Will i be ok to replace my 5850 with a 7950 and keep using the same PSU or am i going to have issues?

Also what happens if you draw too much power from your PSU does it shut down or blow?