Time to upgrade? Suggest best bang for buck components please.

Hello all. I'm thinking or "re-building" my PC. I originally got it put together at NCIX in May, 2007. Antec 300 case | Intel Core2 duo e6750 @2.66ghz | 2gb's Patriot extreme RAM ddr2 400mhz | Gigabyte P35-DS3L mobo | evga geforce 8800 GTS | seagate 320 gb hd sata2 | OCZ psu (over 550W, can't remember, lazy to check inside case)

This computer served me extremely well (still does). Always ran fast, and at the time I bought everything on sale @ NCIX. Was an extremely good bang for buck system. I believe it cost me around ~$1000 at the time. 1st, should I do an upgrade? Is it worth it right now, or should I wait for a bit longer? If I do, I definitely want to RE-USE the Case, the PSU, and the HD for storage (ill be getting a SSD for OS).

2nd, what hardware would you guys suggest I keep an eye on for potential sales, that would be the best bang for buck. I would basically like to a buy a mobo, cpu, ram (8 gb's?), GPU, and a small SSD for $600 MAX. Currently I only really play League of Legends, and I definitely don't game much anymore like I used to, but I would like a system that would handle some future games like HL3, at medium ish settings at least. Not looking for anything cutting edge. Also, something that runs a poorly optimized game like Civ 5 smoothly. Would prefer something "future proof" for the next 6-7 years (this is what i would consider my last gaming/performance pc). I just want a GFX that is comparable to the 8000gts (at its release time). Remember, all suggested hardware I will be keeping an eye out for sales in the next month, so even if everything currently totals over 600, I would wait until there is a deal on the more expensive components.. Thanks! BTW, I live in Canada, and im about a 20 min drive from an NCIX store, so if possible i'd rather get everything @ NCIX.