Sounds like you've done exactly what I've done to my hatch! I went for the perrin CAI, a remap and the full decat on my sti from scoobyclinic and it's very loud, but that's what I wanted! I'm no expert but I don't think there's much more you can do to the exhaust apart from taking the cat out.
I think the only problem with driving it on an unmapped induction kit is you might get an engine management light pop on because of the different air flow rates, but as dipsy said; take it easy (as tempting as it is to floor it!!) and it'll be OK