I was wondering if (for gaming) adding another 7770 in cfx, even though I only have one monitor, will improve my FPS on some games such as Battle field, or Crysis 2. If it does not, what would be the best thing to upgrade? Would rather not upgrade my hard drive, though.
CPU: Phenom II x6 OC 3.9
Memory: 16gb DDR3
Power Supply: 750w
Mother Board: Gigabyte GA-990FXA
Hard Drive: An old sata 1 without a label
I just dropped a 2nd 7700 ghz edition board into my wife's computer, with a CX650 PSU, and performance in Unigene Heaven nearly doubled. It went from 19.2 to 37.8 FPS, with all settings maxed and 1920x1080 resolution. So to answer your question, yes you will see a nice performance gain and your PSU should handle it no problem!
What Lokordd said. Your PC specs just fine for 7700 crossfire. Just a note, you don't need multiple cards to run multiple monitors. I would suggest looking into a better drive in the future. SATA I could be a source of slowdowns in your system in general. Considering SATA is up to III, I'm sure you'll see a very noticeable performance increase if you jump to a more modern HDD, not to mention the leap in performance going to a SSD.
Thanks for the feedback. @drosencraft, Is cloning a drive an easy thing to do? If so, I might upgrade. That was the only worry I have ever had with getting a new drive, I don't really want to lose everything on my hard drive, or mess with reinstalling W7
When I upgraded the drive in my laptop, I used EaseUS Todo Backup Free edition. For doing a simple clone it worked alright for me. I connected to the drive with an external enclosure, but in theory you could just place the drive in your desktop for the cloning process.