MC275s, I own a 1961 and a CE GG, bass is not a problem.. Both early and later models. I use to run VMPS TIIse (2 x 12" bass drivers each).
They can ROCK... Late night listening.. Christal clear too.
A MC240, actually sounds better to me.. 6L6 valve. (I own a pair of those too). Tough to beat the mids with 6L6s. MC30 with 6L6s are tough to beat.. MC60 with 6550s.. Bass is not a problem.. Either one..
4-24 ohm speakers work very well too.. Some valve amps don't like 4 ohm to much.. Macs will tap a 2 ohms, no problems, run HOT, but run fine.
Regards