5870 for $399. It is better than the 470 performance wise, it is quieter, less power hungry and cooler and is not much more expensive. The 470 was designed to beat the 5850 which it did, but then they priced it too close to a 5870 which made it pointless. Despite having used only Nvidia myself for years, there is just no way I can possbily justify recommending the new 400 series for gamers over the ATI 5XXX series. I never thought I would see the day when ATI were better, but the day has come.
Don't buy the ATI 4XXX series, they are good cards but if you are spending money to improve your modern computer, then spend it on new technology not old stuff, especially as more Direct X 11 will be coming out, no reason to buy a card that can't use it.
The choice between a good GPU or a weaker one with an SSD, it has to be the GPU everytime, the SSDs are expensive and not going to give you much performance increase.
If you want to spend less money then go with a 5850, it will play games well on 1920 x 1080 resolution, Crysis is the only one that will likely have to have AA turned off to stay at high settings.