I have almost the same build, except I have a Pentium E2200 @ 3.2GHz and 6GB in mine. I was going to post a thread asking if it was worth buying a Q9450 for like $120 on Ebay.
I get by just fine on a Radeon 5770 video card too. I suppose there's no point in upgrading for me.
The SSD was the best upgrade I did.
I used to run wow (which can get very cpu heavy while raiding and using some addons) on a e2160@3ghz with an nvidia 9600gt (much slower than a 5770).
I upgraded to a q9550 and noticed how much cpu bottlenecked was my gpu, more recent games will show even a bigger impact and my gpu was slower than yours.
To the OP; the e8500 is still a rather sought after cpu, what about selling the cpu+ram+mobo and buying a 5600k apu?
An a10 5800k performs roughly on par with a q9550 or it's a bit faster, the 5600k clocks similarly to the 5800 (4.3-4.6ghz) while being cheaper.
You should get around 100$ for your old hardware and with another 100$ that you planned to spend you'd get a new socket with modern features like sata3 and usb3 support and better power consumption.
Ibn the end you must decide between the hassle of selling your old hardware and mounting the new parts VS a drop in upgrade.
Sata 3 alone is worth it imo.
As soon as AMD releases FM2 athlons you should spend even less since you don't need the igpu anyway.