in order of decreasing responsiveness and increasing power.
GT2871R (56T)>260-270kw, GT3071R>280-290kw, GT3076>320-330kw, and then you go into GT35 teritory which i don;t think is what you are looking for. you then have the choice of what rear housing to use, 0.6* for response and 0.8* for power. Personally i would go for the 0.8* option so you don't choke the power in the top end, but you said your after more punch so you mightn't agree.
EDIT!!
The power figures quoted are rought figures and you will be running more than 14psi to achieve them.