Your specs aren't bad for 2009. By today's standards, though, you're gonna start having some trouble.
EDIT: Ace, your specs aren't too bad either. We both have the same processor.
Finished the upgrade last week. Ended up getting a new CPU cooler and said "F&$% it" and got the GTX 970. With 16GB of RAM I've noticed stuff is much smoother. The CPU is wicked awesome and run waaay cooler than my old one (at a higher stock clock speed as well).
For those in the market for a good GFX Card...I highly recommend the GTX970 (I got an EVGA one). There are a lot of reported problems with coil whine, which I also encountered early on, but after like a day or two it disappeared. When I did have the problem setting the nVidia Adaptive Sync feature seemed to get rid of it.
I had ordered my upgrade parts before I realized DDR4 was out. I partially regret not making a DDR4 system...but my wallet really thanks me. That would have gotten really pricey really fast.
Intel Core i7-5960X Processor Extreme - 8 Cores
Got a little pocket change 'eh? That bad boy's not cheap. Anything more than 4 cores is on my wish list too but the price jump just isn't worth the performance gain.
From what I understand games are optimized to work better on only a small number of faster cores (hence the slow adoption of hexacore and octacore CPUs in gaming). Most games don't really take advantage of more than four cores. Video editing on the other hand...
The i7-5960X (8-core) is $1,050 USD with a base clock of 3.0Ghz. The i7 4790k (4-core) is a 4.0Ghz base clock and only about $340 USD. My bet is that the 4790k would outperform the 5960X in gaming because of the reasons above.
I want to say that I read a benchmark not too long ago comparing a 6-Core intel CPU with an equivalent 4-core CPU and the 4-core had slightly better gaming performance...despite the fact the the 6-core wiped the floor with the 4-core in just about everything else.