Kevs, I wouldn't suggest building a box that will last you for "years". I suggest instead building a box that will plan to last you 18 months but with some options to upgrade if you need to. Some suggestions:
uATX 785g
http://www.newegg.com/Product/...?Item=N82E16813128399
This chipset has been extremely solid and seems to be quite good at supporting 1600 DDR3 memory.
CPU:
Phenom II X2 550
http://www.newegg.com/Product/...?Item=N82E16819103680
For $100 it gives you quite a bang for your buck. Unlocked means easier overclock for a beginner like yourself.
Memory:
G-Skill 1.5v 9-9-9-24
http://www.newegg.com/Product/...?Item=N82E16820231193
Hard Drive:
Samsung 500GB/Platter F3 Series - important for speed/heat/power usage
500GB
http://www.newegg.com/Product/...?Item=N82E16822152181
1TB
http://www.newegg.com/Product/...?Item=N82E16822152185
Video:
ATI 4770
http://www.newegg.com/Product/...?Item=N82E16814125298
Case:
in-win case with 300 watt dual rail
http://www.newegg.com/Product/...?Item=N82E16811108191
In the end it is $600 in hardware (minus the OS, Keyboard/Mouse/Monitor) that will not only last you 18 months minimum *but* also well position you for future updates into the Quad Core and additional DDR3 memory
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J&W MINIX (ITX 780g) Athlon X2 5050e
DFI LanParty JR (uATX 790gx) Athlon X4 620
DFI LanParty JR (uATX 790gx) Phenom II 940
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