Rage has really lightweight system requirements for a modern game. It ought to run smoothly on any good piece of hardware released in the last 4 years.
EDIT: In case you haven't been told already, however, AMD users may want to steer clear of the game until the gaming community has finally given a thumbs up.
It's not that AMD users should avoid the game at all - it's rather that they should be prepared to having to do a bit of driver tweaking on their own to get it to work properly.
But yes, it's a rather lightweight game when it comes the GPU - partially due to a limited amount of post processing or shading (most environment lights and shadows are pre-baked) and some good code.
However it's fairly intense on the CPU compared to other games, and most performance issues can be isolated to this piece of hardware [1] (besides driver issues or things like particle overdraw with MSAA enabled) - the harddrive the game is installed on will take a beating aswell.
It will pretty much put a stranglehold on the drive it is installed to, so preferably don't install it to a drive with a lot of disk I/O already.
1 - From my own tests. With an uncapped framerate, the game framerate in the same static scene scaled almost 1:1 with the clock speed of my CPU - eg. ~120 fps at 3400 MHz, ~100 FPS at 2700 MHz, ~80 FPS at 2200 MHz et.c..