The Mcintosh are just barely into the 20's with 29hz, not enough to qualify in my books. The Krell's well,...... 2 10" drivers will certainly give you 25hz but you had better be using a really good amp. Those 2 big drivers are going to suck the power out of it, those are some big speakers \:\)

Jason
M80 v2
VP160 v3
QS8 v2
PB13 Ultra
Denon 3808
Samsung 85" Q70