Speedup the Mcintosh 2275?

Hello everyone!
Recently I've got an almighty 2275 and I really like it's crisp sound but in my taste it's a little bit slow for d'n'b and limp bizkit which I really want to be able to listen couple of times after norah jones and peter gabriel. So I have KT88 from Black Treasure and 12AT7s by Philips ECC81 from 70s. Is there any tubes which will effectively speed it all up? I really need more punch and maybe more details.

Thank you guys!

BTW, I've NS1000Ms hooked up to 4Ohm outs of 2275, is this correct? Maybe 8Ohms are better? I've measured Yummies with my multimeter and they've showed 5.5Ohm.