"Musical" subwoofers? Advice please on comparing JL subs

Tubeculin,  I don't know what you consider 5% breadwinner prices for gear is, perhaps a Bryston 28B3 pair of monos?   $30K...?   But if $7K is in your budget, you should play with a pair of the Anthem M1 monoblocks.    I think that is the bargain of the new century.   Very affordable for high end, well designed gear and if you can find a used pair like I did, even better (but good luck finding any, they almost never come up for sale).   And if you were not pleased with them after finding them at a good used price, you'd be able to resell and get all of your money back, maybe more.

Slim, Yeah, I’m not able to pay new car prices for amps. My whole system was the cost of a decent sedan, lock, stock and barrel. I’m more budget/value based. These are in my range. But, I’m not in the equipment revolving door game. It took a few iterations to get where I am and I’m staying. I’m in this for the music, not the joy of playing with new toys every few months.

However, Stereophile was not terribly complementary of the M1s they tested (two sets) although their measurements confirmed the marketing hype. Anthem uses PWM.

The bottom line was that the reviewer would not recommend them, yet. The reviewer did expect the flaws found would be corrected with further voicing perhaps over time. Also, I notice there are a lot of digital components in the circuit (not signal path) that have the potential to add digital noise. I think in a home theater setting they would do well (these amps are out of my price range for TV audio as well). And, they use a PCB not P2P wiring. So overall I probably wouldn’t audition them if I were into an equipment change.

I hope that you continue to enjoy yours. I’m glad they sound so good to you.

FYI: How a Class D "Digital" Amplifier Works

https://www.audioholics.com/audio-amplifier/class-d-digital-amplifier

Tuberculin,
This might be a better read to explain Class D vs. Class A or A/b
https://en.wikipedia.org/wiki/Class-D_amplifier

You can read how Class D is not a ’digital’ amplifier. It’s simply a full on or full off output device vs. a full on all the time device. Theoretically it can achieve 100 percent efficiency, but with the available devices it is not that high obviously, more like 90 plus percent. Class A amps have a theoretical efficiency top of 50% and as the article states often they don’t even hit 20%. But Class A amps make for fabulous winter time axillary home heaters or summer time A/C test appliances. Class D amplifiers using sophisticated feedback design and equally sophisticated power supply design not only deliver incredibly high output power with very little losses going into heat, but they move any distortion (by design) out of audible ranges. This is why a nicely designed Class D audio amp can be so incredibly smooth, powerful and not very warm to the touch with amazingly low power consumption in the idle mode. I think that my 2000 watt per channel M1’s draw only 3 watts in standby and 13 watts when in full on operation at idle.
I tried to get a copy of the schematic of the M1 from Anthem as a buddy of mine who is an excellent ex-Bell Labs electrical design engineer wanted to study what they employed. Anthem told me that they do not supply technical design data on this amp to anyone as it is extremely proprietary. The guy at Anthem told me that they invested over $5 Million dollars in the R/D engineering of the circuits and they don’t wish to share it with any competitors. I suppose I fully understand this. B&O on the other hand developed their Class D ICE modules for general distribution to manufacturers who wanted a quick and easy way to build Class D amps at very reasonable cost. This is why most amps in Class D on the market are using ICE power modules and why they are great for Sub woofers where high frequency harshness is not an issue, but powerful low distortion Bass frequencies work well.
I did have the opportunity to test and evaluate the Parasound Zonemaster Class D amp. They sent me one to try against the A51 and the M1’s. The Zonemaster is a very nice compact, 600 watt per channel amp. It actually plays very well, but for my ears, it had that well known high frequency harshness due to the inexpensive ICE modules. But it only costs $1200 dollars for a 2 channel 600 watt per channel amp! I told the guys at Parasound that as much as I enjoyed playing with the amp, it was not in my opinion well suited for a very high end audio system with high resolution speakers. I said it was absolutely perfect as an entry level amp for people just getting started and on a budget, or for college kids who want a lot of power in their dorm rooms and who have to move around often as its so light and compact/easy to move; or as an amp in a home theater requiring more channels to drive surrounds or rear speakers.  People using lower cost speakers which are not going to be extremely resolving in the upper frequencies might not even hear any harshness. They got a laugh out of that and said I had actually hit it right on the mark in terms of who their intended market was; so they were very pleased that I was in agreement. They never expected it to be competitive against the likes of the M1’s. But the Zonemaster blew away the A51 Halo in lower end, lower/mid grunt, that thing has some balls. It just was not as smooth in the upper mids/upper range as the A51. A $1200 Zonemaster vs. the $5000 A51 did pretty decently overall though. If I was back in college in my dorm room which was set up like a party/disco club, I would have been the place to be hanging out had I owned the Zonemaster back then vs. my old tube amp. But then again the speakers probably would not have made it through a weekend.

When it comes to high end amps, I think from what I am told the Bryston 28B3 monoblocks at $30K are about as good as it gets. I chatted at length with Ian at Axiom about the 28B3’s vs. the M1’s. He has heard both quite a bit and he told me that they are both top of the line, but he likes the massive reserve power of the 28B3’s and those are his go to amps. I of course pointed out that he is talking in terms of money being no object and he agreed. I asked if he was doing a value comparison, that is the $30K 28B3’s vs. the $7K M1’s, what would he do.... he said the M1’s would always be his normal second choice, but when I put it that way, he’d definitely go with M1’s; they are very close in performance. So there you have it; a well designed Class D amp pair against the some of the best in linear high dollar monoblocks is right in the running. And I am not heating the house with it or paying large utility bills.

As far as a sub amp goes (or run up to ~1kHz) the Class D-based Crown K2 is as good as any I've heard. When bridged it's supposedly a fine all-round amp not restricted to subs/lower to central midrange prowess only. 

As great stand-alone all-round amps costing less than a fortune the Crown Studio Reference I/II (now discontinued) and MC² Audio S800/1400 are highly recommended. Money placed where it matters.