What is low end / bass like MC 275 McIntosh tube amp?

Just curious. I’ve only heard the 275 at low volumes or with bookshelf speakers. The mids and highs sound really smooth. Compared to a SS amp, in general, does one lose much low end? 
It’s relative to the speaker that is being used. But, newer McIntosh tube amps enjoy the benefit of the use of a stable wide bandwidth unity output transformer, which greatly enhances overall performance to include bass. The new 275 has 4, 8, and 16 ohm taps which allows for impedance matching to whatever speakers you are using. 
Although not a MC275, my MC2301s mated with my older 89db efficient B&W 800 Nautilus speakers had great deep non muddy bass. 
I believe that with the MC275 and its various output taps, and the stable power that it is known for, you will be enjoying music. Remember that bookshelf speakers can only produce so much bass...and depending on the size, you are already at a deficit of bass capability based on size alone. 

IME, your bookshelf speaker and it’s size will be a major factor in how much bass is produced. I have used Radio Shack bookshelf, B&W bookshelf, Klipsch bookshelves, and no matter if a tube or solid state driving them, the sound of bass coming from the bookshelf seemed to be repeatedly the same. I liked the old Altec or Advent bookshelves which seemed to have a kick to the bass. 
I run a 2.1 system with ZU Omen defs. With the sub, I do have some control over low end if I need to boost or lessen a bit.
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.

I have mc501s and mc275. I normally bi-amp with the 275 doing the mids and hi’s. This sounds awesome. For kicks one day I compared the 501’s vs. the 275 on their own. I was surprised how well the 275 did, it was maybe 5% less than the 501s until you really pushed the volume way up