Kisianik :
Dell BIOS is locked, so overclocking here is very difficult - pinmode and with PLL number, too bad.
And about a few $$ means more like $400 and up or so. Just an opinion.
I'm aware that it would come to around $400 including the GPU, but he was planning a GPU upgrade anyway (possibly could have been looking at 7870/660 area if the CPU could keep up).
That being said you can find a budget case, power supply and cpu cooler for $200 or maybe less. If he really wants to squeeze performance out of this thing then that is truly the only option.
This would be a good combo that has a $35 MIR as well....
http://www.newegg.com/Product/ComboDealDetails.aspx?ItemList=Combo.1297427
My personal opinion is that I wouldn't waste time unless you have grander plans with the setup. If you just want this to get you through, all the parts can be used in builds later when you decide to retire the Q6600.
I think of the 7770 option as a sinkhole. You are not going to want to pair that up with any modern CPU unless it is to play a specific game like Star Wars: The Old Republic or another game of that ilk (MMORPG). It will still play present-day games, but not at higher settings, and will likely struggle in the future.
All of these opinions are based on the 1920x1080 resolution, so the lower resolution you are playing at, the more the 7770 makes sense.