"can I get the max performance of the Radeon 9700 with my system"
No. AFAIK there are no cpus available that make the R9700 the limiting factor, rather than the cpu, so you can't get "max" performance. You'll get very good performance though.
More importantly, watch how a bunch of guys will now post that you should buy a 9500, or a Ti4600, because "you will be wasting your money" because you didn't buy a cpu as fast as theirs, and they want to brag about theirs. If I had a $100 for every time I've seen this (and laughed about it) I would not be going back to work this afternoon.
The posts will read something like" I would get a R9500 Pro for your system. I have a P4 2.8, and I am barely able to scratch the R9700's mighty potential. You will be cpu limited with your 2.2GHz."
I bet that even though I've pointed this out, the urge to brag will be so great these guys do it anyway.
Oh well, grab a beer, make some popcorn, and laugh at their folly.
BTW- I had a 1.4GHz Athlon XP and went from low 8000s 3dMark 2001 with a Ti4400, to low 11000s with a R9700. (and I could for sure tell the difference in gaming)
So don't let the "I bought a fast PC so now I'm an expert" crowd confuse you- your system will get a big boost whatever you have.