Best 80-100 w Amplifier Available Under $4k Used?

So, I have a somewhat complicated dilemma that I've fallen into. For the past year, and prior to this weekend, I was extremely happy with my current system, which is composed as follows:

Silverline 17.5 speakers
Atma-Sphere S30 MIII.5 amplifier
Meridian GO2 Preamplifier
Meridian G08 cd player
Olive D4 Music Server
Bryston BDA-1 DAC

A good friend and audiophile, is moving to a significantly downsized home. He has always been very impressed with my Silverlines and was considering them as possibly the best option for his smaller listening area in the new home. He wanted to hear what they would sound like with his electronics, and yesterday, brought over his Plinius SA-103 amplifer and inserted it into my system in place of the Atma-Sphere amplifier. Given that he also has a GO2, a G08, and we also share the same speaker cabling, this essentially recreated exactly what he would hear with them in his system, although his new room is just a bit larger than mine.

Hearing the 17.5's with the Plinius was a bit of a revelation. Not entirely, or even necessarily because it was purely better than my S30.5 in terms of overall sound, but the Plinius drove the speakers with so much more command, and opened them up in ways I had never before heard. The slam was immense, and I was shocked by the quality of midrange from a solid state amp. The highs were also extended and extremely impressive.

At that point, not being sure if it was just the quality and performance of the Plinius that made the difference, or the additional power reserves, I made a request of my friend. He then went over to his brothers nearby home, and borrowed his Monarchy SM70 Pro monoblocks. We placed them in my system, in place of the Plinius, and while they clearly did not compare to the Plinius, there was again, a sense of greater openness, more slam, and more control than with the S30 when we switched it back in. While we both preferred the Atma-Sphere to the Monarchy's, it became apparent that the significant additional power in both solid state amplifiers was able to drive the speakers to greater heights in some important ways. Oh, and before I forget,as a reference point, I was still quite impressed with the Monarchy amps. For the money, these offer absolutely remarkable performance. They simply are not in the class of the Atma-Sphere, or the Plinius, but at a quarter to an eighth of the price of those units, how could they be expected to be?

So now you have the beginings of an understanding of the quandary of where I find myself now. My previously happy world listening to the system with the S30 MKIII.5 has been disrupted and I do not think I can move forward without addressing it. An easy answer would be to move to an upper level Atma-Sphere, and I would not hesitate for a moment to do so, but two things absolutely prevent that. First, I could not possibly afford an MA-1,even used. Secondly, my system is in a small room, and the heat from a pair of those would literally provide sauna like temperatures. I even have to abstain from using the S30 on very warm days in June, July and August (when I necessarily move to my headphone system).

And so, I'm left wondering what the best options are. From the sale of the S30.5, and a couple previously completed transactions, I could fund an amplifier in the $3500-4000.00 range, with an absolute hard limit on $4000. max. I would also clearly plan to buy used to maximize what was available to me. And, having experienced the listening session I described above, I would need an amplifier in the 80-100 wpc channel class.

I've long been an avowed tube lover, although the Atma-Sphere's are amongst the least "tube like" tubed amplifiers I have experienced, they simply sould like music, to me. I am not aware of any tubed amps of the stated power which would fit into my price range, excepting possibly the Rogue M150-180's, and I've heard those and found them a bit dry in character.

That would seem to leave solid state as my only likely option? Obviously, a used Plinius SA-103 is more than I can afford. I could however, purchase an SA-102, and hope that model is close to the 103 in performance. Other possible options could be the Modwright KWA 100SE, an Aesthetix Atlas, or even a pair of Parasound JC-1's. But I'm honestly getting into waters here that I truly don't know, with too many possibilities that I've not heard and do not otherwise have access to experience.

Your thoughts, expertise, recommendations and advice as to my best options would be greatly appreciated.