Well first of all you should have the common sense to at least check in your task manager/msi afterburner (or evga precision x, etc some hardware monitor) to see if anything is actually bottlenecking you.
But there is no reason why you should lag in tf2 with that setup. If this were for other games, I would say ugrade the gpu. For video editing the 650 should be fine (Look up adobe's cuda hack if you want gpu accel for premiere/ae/etc, don't think the 650 ti is natively supported). A 3770k or 4770k (or higher) would probably benefit for video editing, but honestly it's not worth it unless you do a ton of it. If you were building a new pc and hadn't already purchased the 3570k that'd be different.
Have you tried overclocking? Defrag hard drive? Updated drivers? Verify cache? I really doubt the problem is going to be hardware.