As for wheels for the PS3, Logitech has a less expensive wheel called Driving Force GT wheel. I've tried it and it's pretty good. Better than the subpar Microsoft wheel for the XBox 360. But then again, it retails for $175 bucks, and I think I got my Microsoft wheel for something like $100.
In the end, I traded it for a G25 (previous generation) - never regretted it even though it costs twice as much, as its quality definitely makes its price worthwhile IMO... If I were not using it to do things like the driving school in GTR2 and other simulation games though, I don't think I would have bought it... The graphics in Gran Turismo Prologue were out-of-your-mind-jaw-dropping-stunning.... but I really didn't feel like the physics of the game made it worth it to buy an expensive wheel. Maybe if GT5 has much improved upon physics... I guess we'll see...