Hi all. My current system is getting long in the tooth and in need of an upgrade so I’m trying to figure out the best bang for my buck as I’m on a limited budget.

My current specs are:
Motherboard: BIOSTAR TA-790GX A3+

CPU: AMD Athlon II X4 630 (stock speed 2.8 Ghz , overclocked to 3.08 Ghz. Can’t seem to get it any higher. Should I be happy with a 10% overclock?)

Memory: 4 GB (2 GB x 2) of OCZ3G1600LV2G

Graphics: SAPPHIRE VAPOR-X HD5770 1GB GDDR5 (not overclocked but will be soon to try and get the most out of it I can).

Harddrive: WD 1 TB drive, nothing special. I recently bought a 64 GB Crucial SSD I will be installing for OS.

CPU Cooler: Corsair Hydro H50

Current Hardware Considerations:
Upgrade CPU to AMD Phenom II X4 955 Black Edition (~$110) and overclock it as far as I can.
Or
Upgrade Graphics card by either adding a second HD5770 (~$110) and run in CrossFire or replace my HD5770 with a Radeon HD 6850 (~$150)

Note primary usage is gaming at 1920x1080 with AA x2 or x4 and moderate to high game settings.

Other questions, can I run a HD5770 and HD6850 in CrossFire together? If so would everything slow down to the 5770 level of performance?

Thanks in advance for any feedback!
Paul