5850 PSU Needs

And would my Phenom II X2 550 BE be a bottleneck?

Your CPU will hold up quite well, however your PSU only barely passes. By that I mean it lacks the necessary two 6pin connectors needed for the 5850. Not that it is not powerful enough, one 5850 need 500w and crossfire 600w, which obviously your 650w passes with flying colors. It is mostly recommended that your PSU have the necessary power pins to run the graphics card, you can use those 4pin Molex to 6pin adapter cables to get your two 6pins, just be sure to spread the load out over both strands of 4pin Molex’s for best compatibility and stability.

edit: spelling

You are mistaken sir!   It does have two PCIe 6 Pin power cables. I am currently running two 9800GTs and both need a 6 pin PCIe power connector. What I need to know is the amperage needed on the 12V rail and if my PSU can supply that.

Interesting to hear. Thank you sir.

Ya your right, it has a 6 and 6+2 pin. I was looking further down in the features section looking for how many pins it had. Seems im off my ball today.

No worries at all. I was of course joking around with you and hope you didn't take the comment as rude. I have many of those days.  

Your PSU is more than sufficient.
HD5850 in spite of being so powerful takes lesser power than a HD4850

Good Luck!  

^ +1

I have a 5850 @ 850/1200 on an Antec TruePower 550w and its perfectly fine. You should be ok as long as you have nothing else drawing an extraordinary amount of power.