Thunderbolt Audio interface for garage band

A good place to get started is HangTime's FAQ:

http://www.bulletsandbones.com/GB/FAQPages/Interfaces.html

You should first decide how many inputs you need and what kind of inputs. Then choose a budget.

Is there a single input option?

Do you mean a single mono input or an LR stereo pair single input?

If you only need one input, why not just use the line-in on your Mac?

well they stopped putting the minipin input on these new imacs. Doesn't that suck?

I went to newegg.com and got this ordered this.

SYBA SY-AUD20091 USB Audio Adapter.

Thanks for your reply.