Debating between Mcintosh SS or tube monos.

The MC2301 certainly does not lack bass…it’s the amplifier speaker combination which causes the perception that bass might be lacking. I used to drive B&W N800s with an MC2301 with great bass control and authority. The 800s were inefficient (89db) which caused me to turn the volume up to play decently. The bass was incredible though. The Mc2301s were very warm to the touch at constant 100 plus watt listening sessions. I now have field coil horn speakers, Classic audio Loudspeakers T1.5 reference which are way more efficient  (102db or so) and much much larger than the 800s..the bass is dynamic, deep, and articulate. The MC2301s run cooler now since I only need 30 watts to create a rock concert experience in my previous room, 30x20x8. Only occasionally did I crave extra bass if I waned to add club or rock concert feeling into my listening space. Otherwise, this combination is excellent. I have heard the MC501s, not the 611, but these are great products as well. If you do go tubes, then you must accept that tubes must be replaced every so often as they have a tendency to lose their luster and listening qualities as they are used over a period of time. This is of course dependent on type of tube and how long your listening sessions are. Using efficient speakers with a tube amps is an ideal combination. I believe generally speaking that If your speakers are not efficient ,you will not be happy with a tube amp. There is a lot more to inefficiency and driving speakers like this with tube amps. I know of two tube amps that drive speakers to room shaking bass with the speakers I mentioned, the MC2301 and Atmasphere NOVACRON. Of course there is a lot more to efficiency, but the pairing of speakers with whatever amp you decide on is crucial to obtain the best quality of music.