Wow, I am envious. The big and beautiful Avalons. Maybe I can bring the amps and aesthetix preamp and you bring the speakers and we can have quite a concert. 8-)
As I recall from following the Avalons over the years, the Ascent and then later the Eidolons needed powerful amps, typically reported ss amps, to really come to their full potential. But with the big Avalons, don't these have the subwoofers with accompanying sub amps? If so, these speakers could be much easier to drive than their smaller sibblings. None of the Avalons have any nasty dips in their impedance curves which makes it equally nice. This opens the door for consideration for either the JL-3s or a pair of JL-2s.
I have wanted to hear a head-to-head of the two CAT amps but logistics have just not allowed it .... yet. Maybe I will get the chance this year. But in this case, it would be the JL-3 sig vs JL-2 std models which both have the same capacitor types. Here it would come down to the potential of greater dynamic contrasts, ease, perhaps low-end control, etc., rather than much if at all any tonality or resolution differences.
The JL-2 Sig has the latest cap changes as does the JL-3 Sig MK II. These model suffixes get to be a little complicated! I have held off with the MK II update only because of the concern of shipping the amps back to CAT. This is almost something I would deliver myself to avoid the potential of damage. And for now, what the JL-3 sigs do for me leaves me little wanting for more tweaking to them other than getting the updated circuitry to better handle tube failures. And a CAT dealer can do this with some parts changes. I understand this latter work is standard to all CAT amps delivered now.
In my smallish room, 13x18x7.5, the single JL-2 would be plenty to bring happiness with the SoundLab A1s. But I bought the JL-3s with the intent of them being my last amp. I have bigger and greater plans for a larger room in the future. And I have felt that it would most likely only be Avalons that would displace the SoundLabs from my system. So I bought the JL-3 with all this in mind rather than to my specific needs at the moment.
With the money you are looking to spend, and having premier speakers in this wonderfully sized room, you need to find a way to hear these amps for yourself. A single JL-2 might be a good start if cost is an issue. But ideally, you will want one amp per speaker to truly get the separation and subtle details that I have no doubt your speakers are capable of. And then it comes down to a pair of JL-3s driven full range or a pair of JL-2's biamped. There's just no way to know how the outcome would be unless you tried it right then and there. I would love to have the opportunity to hear this. Either way, it's the same number of tubes so plan on listening to your music in summer clothes. 8-)
John