Benchmark or McIntosh....

@jasonbourne71 https://www.powersoundaudio.com/collections/subwoofers?filter.p.m.custom.woofer_size=21%22&filter.p.m.custom.woofer_size=21%22+IPAL

@curiousjim Room is 22x12x7 give or take a few inches.

@mm1tt77 100% agree on the McIntosh resale. It would be a pretty easy proposition. Krell on the other hand...would probably make the room into a sauna.

@panzrwagn You are spot on. I just am reluctant to change everything out. I could probably just change the front LRC and live with it. Something with more efficiency would help. 86/87db on the current monitors.  

Definitely considering Parasound monos, Musical Fidelity monos. Wadia monos. I looked at some others (Krell, Mark Levinson, Theta, Mola Mola, Wyred 4 Sound and others.

It appears some of you are not buying into the concept of multiple 21" subwoofers.  Isn't being an audiophile about taking it to extremes?

Sell the NHT's and buy the biggest pair of Sound Labs ESL's! Nothing as realistic as having square feet of sound radiating surface!

My MA8900 never runs hot. I don’t think it lacks detail either. I find it to be an excellent balance of smooth and detailed. I’ve heard the 611 and 1.2 in a dealer room and I’m sure they would be an upgrade but I’m really happy with my setup at the moment and honestly they would be overkill in my small listening room.  I remember hearing some NHTs years ago and really liked them a lot.  Listen to all of them, buy what you like.

Hah - older Krell gear for sure.  The new Krell Amps don’t run hot at all.  For what I think you are looking for out of the amp, Krell and Max’s are the 2 American Made brands that really built their reputations on being able to drive almost any speakers, even 4 ohm or speakers that dip into the sub 4 ohm realm.  They went at if in different ways, Mac with their proprietary process that promises to deliverer stable power across the spectrum, automatically matching the need of the speakers, Krell designs their Amps to double down on power as Ohms drop.  By no means are these the only 2 that offer Amps are designed to drive difficult loads, they are the 2 most well known for it.  Hegel would be another great option.  Music Fidelity would be another along with Parasound.  If it’s drive and power, as others mentioned, the new Clas D amps deliver that in spades, run cool, more compact footprint and efficient.  No experience with the new Class D and not everyone falls in love with them, seems to be you either really love their sound or prefer Tube or old school SS Class A or AB amps.