Tube amp Low end Bass question

Those Omen's will sound amazing with a tube amp.  You need 15w to 18w to drive them well with plenty of headroom to hit 105dB for music.  

The MC275 is a lovely amp but you will find a SET will sound heavenly in comparison and your speakers are more than efficient enough to be driven by a SET in any normal size room.  

Two subs are not essential but it will improve balance.  Key is getting the crossover point and placements just right.  I have a SET amp and two 10" subs paired with standmount speakers.

There are some relatively high powered SETs but the more power the pricier they get.  What is your budget (the MC275 is $5750)?  Do you have room above that?  Stereo or mono-blocks?  

I sell SET and Push-Pull units for Art Audio but my stuff is a bit pricier than Mc and is relatively low power.  I can help steer you toward something that is a better fit though.  What part of the country are you in?  

Also, the above comment on 845s and 211s being kinda scary in a SET stems from them running REALLY hot.  I agree.  Quality is critical.  You want separate transformers for the heaters and audio circuits and placement of internal parts has a big impact.  Designed right they only run a bit hotter than a push-pull.  Designed poorly it is like having a space heater in your room.    

You could consider trying a SET from one of the retailers who offer it with a generous return policy. If it is inadequate, return it. Usually you are risking $75 in shipping charges.

I doubt a 300B SET will deliver enough power but an 845, 211, or maybe an EL34 will give you enough power.  

As a fall back, he MC275 is a nice amp. 5w less in power will have no impact on your headroom with those speakers. The Zu Omens are really easy to drive. The issue is, if you don’t like it you are usually risking a 20% restocking fee. At least that is what the retailers I have asked will charge me.