From personal experience, I can't recommend a whell strongly enough.
(Yeah, it's not suited for Photo Mode, and works but is far too bulky for B-Spec, if you're driving you want to do it with a wheel.)
Don't know where you're at, but Gamestop as others have mentioned is always a solid choice (and it's my first choice for PS3 stuff).
Guess I'm fortunate that I have three Gamestop stores in my town (and no, I don't live in like Manhattan or LA or some major metropolis, I live in this little border town in a state that doesn't have a sales tax, so it's an out-of-state shopping destination to our neighbors).
I pre-ordered my copy of GT5 as soon as the 11/24 date was official, and was able to grab a DFGT right off the shelf at the Gamestop I arranged to pick-up my pre-ordered copy for $130.
I haven't plugged it in lately and switched to B-Spec, but the wheel is calling me. I'll need to deal with tightening the legs on the end table I was using as a mount for my DFGT (because I've been a little too vigorous and have started to make the table a little jiggly), but I'll see if I can get it kicking this weekend!
It's just not the same with the DS3 controller. Steering was a little weird at first, but I just can't get the precision dual feathering of the accelerator and brakes the same as I can with the DFGT wheel.
Without the wheel it's just B-Spec and Photo Mode for me. Don't miss out on the immersion factor and experience - if you can manage it!
Peace...