I'd be careful about planning on overclocked system if you want it to last, overclocking may get a faster performance, but it'll take years off a processor, if you're going for a long-lasting system you're going to want to keep the temperatures down, the cooler you can keep it the longer it'll last.
The average lifespan of a cpu is 10 years. Heavy overclocking may take off 4-5 years. If you are overclocking, typically you're not going to stick with a cpu for 4-5 years, rather, upgrade every 3-4. If you're not overclocking, you're probably going to want to keep it for a while, as it was meant to be.
Also, second on the 5770. It's as good as a 4870, but with much less power, and DX11. As for socket 775, it's a dead socket. However, if you're not going to upgrade the computer, there's no sense in ruling it out. The E8400 is a beast of a processor, but so is any of the comparable $167 AMDs, and AMD finally has processors which match their power (it only took them a year). The i5 is currently the best buy for intel, but it's $200 plus a royalty for the brand new motherboard socket, making it not really that worthwhile, and by Ex's standards, completely useless since it can't use triple channel. IMO the e8400 is overkill for anything but some serious gaming. I bet a Regor would do just fine.
Here's a combo for $181 which comes complete with a not quite top of the line case or power supply, with excellent µATX motherboard and decent cpu, and decent enough ram (4 GB of ddr2 gskill). IMO, this is a ridiculous deal.
I use a CM 690 and recommend them to everyone I meet. You will not find a better case, END OF STORY.
cm 690 - $74 SECC and ABS PlasticPC-K7B - $60 SECC and AluminumHey, look, I found a better case. Zero ricer, and no plastic!
"Parliamentary inquiry, Mr. Chairman - do we have to call the Gentleman a gentleman if he's not one?"