Guys before you can think about weaponry, you have to think about the ships role.
If its designed as a nova replacement as some suggest, then it is primarily a sience vessel and I see no reason for it to have quantum torpedoes at all.
Enhanced sensors; yes, enhanced propulsion; yes, but fitted out with quantums because they're the best in the arsenal? Come on its just a waste of resources.
As for the torp rate, I agree with DT mostly, the forward tubes should fire two torps a peice with a nice long recharge time and the aft ones should fire one a peice again with a nice long recharge time.
Also DJ, I like the impulse housings apart from the front bit were they are joined to the hull, maybe make them a little more flush like the sovvie?