Value oriented upgrade path?

[TheProudNoob]

My specs:

MSI P67A-GD65 (B3)
Intel Core i5-2500K (Cooler = CM Hyper 212+ w/Scythe Slipstream Fans in Push/Pull)
MSI R6850 Cyclone PE/OC (Manufacturer: 860MHz / 1100MHz; Custom: 1000MHz / 1150MHz)
G.Skill 16GB (4 x 4GB) DDR3 1333MHz CL9
Mushkin Chronos 120GB SSD
Samsung F4 2TB

If you look up the motherboard on Newegg, you can see that I chose it based on its flexibility concerning crossfire and a PCIe x1 soundcard. My main issue is I have no idea how to upgrade without being extravagant and wasting money. For instance, if I were to buy a newer generation card (think GTX 6xx series or AMD 7xxx series), I would have a card that I can't use anymore, and I can't sell (don't have the correct packaging). If I crossfire another 6850, I might end up simply wasting money, because the newer gen cards don't cost that much more (when on sale).

I don't have much money. What's a recommended upgrade path for a PC gamer who needs his tech to last all of his college (4 years or more) without any major upgrades?

 

[Aristotelian]

Why do you feel the need to upgrade at all? Your PC sounds like more than enough more most needs and you don't say that there is anything you are doing with it that isn't working. As they say, "Don't fix what ain't broke."

 

[TheProudNoob]

Well, I'm an overclocking enthusiast and a general techie. It's in my nature to plan future upgrades and squeeze the last drop of performance out of the tech I have.

"Don't fix it if it ain't broke." doesn't apply to me

When I was first building my computer, I had to compromise on GPU performance for CPU performance. I went with the 6850 over a 6950 (my optimal choice). I also got the i5-2500K over an AMD Phenom II x4 Black edition.

I always plan my upgrades as far ahead as I can. That's what I'm trying to do here, since I can see that my technology is aging.