I have a gaming PC that's about 5+ years old, but has been updated. The system hasn't really been too slow for me, but it's old and I have a $400 upgrade budget. I play FPS, RTS, racing games at 1920x1080. Also do a bit of video encoding, but that is secondary to gaming.
Where should the $400 go? I'm thinking the CPU/mobo is the bottleneck, but is it? Would a newer GPU be better? I'm not dying to spend it, so I could wait. I could get an i5 3570K + mobo and 8 GB RAM for my budget, but is that really my bottleneck?
Intel Q6600, OC'd to 3.12 GHz
MSI P35 Neo mobo (not SLI) with 4 GB Corsair RAM
Radeon 5850 1GB, OC'd to 900 MHz
Creative SoundBlaster Fatal1ty
Corsair 650W Power Supply
120 GB SSD for Win7 64-bit OS, plus 3 SATA drives (500GB games, 1TB files, 500GB backup)
23" monitor 1920x1080
There's benefit to be had from both CPU upgrade and graphics card upgrade, but I'd recommend upgrading the CPU first - a powerful graphics card would likely become bottlenecked. It's a good CPU (I used to have one too) but Nehalem (the original i3/i5/i7 architecture) was a major step forward in performance. Sandy Bridge and Ivy Bridge have further refined that, so there is a decent performance benefit to upgrading.
You're probably already aware, but you don't need the K model if you're not overclocking. If you leave it at stock speeds then an i5 3450 will be just as effective. If you decide to go down the graphics card upgrade route, the GTX670 would be an awesome upgrade, or GTX660 would deliver more bang for your buck and leave a fair bit of money left to go towards the other upgrades when you decide to buy them (but obviously deliver a bit less future-proofing than the GTX670).