I'd say go for the AMD, it's coming up as a SERIOUS competitor for Intel, and is, in my opinion, better-performing than the intel..
As for the processor, since I am out of touch with the current market prices, I cannot give you good advice, but if it's much cheaper than 3000+, you can go for something like 2400+..
Higher end graphics card suggests that you're a gamer, and the processor is not going to make a big difference if it's greater than 2000Mhz..
From personal experience I have seen that the nVidia chipset is better than the ATI in the same price range, and while you're at it, go for MSI manufacturers.. I'm not sure, but some graphics cards come with TV tuner, so you don't need to buy a separate one..
And by the way, I think it's better to go for a new computer, than upgrade.. If you're upgrading, you'll have to upgrade everything to support the new components, including maybe a new power box.. You'll be able to retain your drives, though..
JaX