The 97-05 Imprezas use a completely different exhaust than the 06-07. But you're correct, the 06 & 07 are identical.
That said, the SPT is a waste of money. I'd go with a used STI axleback.. that will get you a little more volume, be super cheap.. as CF-Ninja says it looks better. Whatever you do, don't put a loud exhaust on it. The equal length OEM header on the 06-07s is good for some power, but sounds awful.