I recently got a Mesa TT-800 amp head and have 3 cabs. A Mesa Subway 2x10, a fEarful 15/6, and a Ampeg SVT410HLF. All sound great, and staking the 2x10 on top of the 4x10 is really amazing. My conundrum is, that I feel I should trade the Ampeg 4x10 for another Subway cab. So if I stack another Subway cab with my 2x10, should I pair with a 1x15 or a second 2x10? I play heavy rock and metal, and blues rock. I play mostly 5 string and drop tune 1/2 step so it's low B flat frequencies. My main band is really loud running 2 100w guitar 1/2 stacks and pounding drums.