AMD is hard to beat in terms of value for money. It really depends what you're using the system for. If you play games and surf etc without much else, an AMD chip would be just as good as any intel, and probably only a few frames difference in the real world, whilst being significantly cheaper when you include the motherboard (think Phenom II X4 or X6).
If you do lots of video encoding, the X6 CPUs are still good, but probably just pipped by the raw power of a high end intel CPU such as the i7 930, though this has a frankly useless upgrade path, so not even close to being 'future proof'. Still, it may have all the power you need for the next few years. I mean, even a Q6600 is enough CPU for most tasks nowadays, you could buy one second hand, overclock it to at least 3.4GHz and see some really decent gains. If your motherboard supports xfire (and the PSU is up to it) you could add another 5770 for a fairly awesome rig without much extra cost.