A little help please

My room is 13' x 21' x 8.5' ceiling. Speakers are located along the short wall about 12-18" off the wall. They can't come out as they'll block an entrance way.  They are about 4' from the side walls. 

Currently I have a Prima Luna Classic Integrated with their standard tubes. Source is Rega Apollo R, MMF-5/Clear Audio Nano V2, or Proton DAC. Speakers are Totem Arro (no mass laoding).

I realize that my placement isn't ideal and my wife's need for decorating balance with furnishings,etc require some trade-offs but I just don't think these speakers are up for the job in some cases. Some songs, like acoustic blues, female vocals, even piano sound great but I'm sometimes finding other recordings seem to sound muddy and there's no real pop and umf on some drums; like I'm hearing music but not feeling it some times.

The totems are not mass loaded. I have heard that mass loading them will tighten up the bass. I could also try some different tubes, but overall I'm not sure either or both will make that big a difference. Which leads me to a discussion of a sub or some new speakers.

I lean towards new speakers.

Possibilities (depending on what I can get my wife to agree to in price and size) are:

PSB Imagine T2, Quad 25L, Revel F206 - As noted above there are decorating issues. A sofa is located about 2.5 feet in front of the right side. As it is now imaging is good, my concern with these is they all have some low driver positions that will be an issue unless I can relocate. Relocating to the long wall is an issue because I'd have to straddle a working fireplace as well as other considerations. 

A larger Totem Forest - leaves me wondering if I'll have similar issues with bass.

Audio Physic Tempo 25 (NOT the plus version) - demo from my local store.

Vandersteen 3A - Signature - also demo from my local store. These are likely too big for my wife's taste; and quite possibly my amp.

  One thing I didn't note so far was the possibility of a sub-woofer.  I'm not thrilled with the idea but I haven't given it an ear so I can't say.

Thoughts anyone?

Thanks for reading and taking the time to respond, Jetson.