In need of a new laptop

It's pretty simple. Get the 15" standard model with 2,0ghz and upgrade the harddrive to 7200rpm if you like to use it mainly for recording and watching movies. If you want to use it for gaming also, get the 15" standard model with 2,2ghz and a 7200rpm drive which comes with a 1gb graphics card.

The only difference between the 15" and the 17" models is that the 17" has a bigger monitor, an additional usb port and an expresscard slot, while the 15" has an sdxc card reader instead.

Since the 15" models all come with quad core processors these latops are more than perfect for recording and mixing, taking into account that most audio interfaces work rock solid under osx.

You could also have a look at other stores besides buying it from apple directly since you might get better payment plans.
 
Probably not, but still I would go for the faster drives anyway. You never know if you need to record something onto the internal harddrive.