Can I replace my stereo with an aftermarket touchscreen one?

So I don't feel like forking over the cash for the prius touchscreen GPS/stereo option. Is the spot where the original standard stereo sits the standard double din size that aftermarket systems are? I understand that it might be some time until aftermarket cable connections make this possible, but im in no rush...and in my opinion i'd get a much better system for less $$$.

One more thing that might be a deal breaker, on the basic unit, are there any controls that would be given up if I replace it with an aftermarket unit that pertain to other controls not releated to sound/GPS?