Emotiva XPA-1 or Wyred SX/ST-1000

I have tested several amps to drive a pair of JBL M9500's, the best of their K2 series that listed for $40,000 in the late 90's. Each speaker has two 15" Woofers, stagger-tuned in separate enclosures with a compression driver/horn between them and weigh over 300lb each. Your L300's have similar heavy woofers and compression drivers, so my experience described here should be relevant.
I have tried Emotiva XPA-1s on the woofers and found that they cannot accurately control them, with bass more boomy and less defined. The heavy woofers require a high damping factor, which is the ratio of circuit impedance (ohms) to amplifier internal impedance. A higher number indicates that the "rubber band" connecting the towing vehicle to the trailer is stiffer. Speaker cables are part of the circuit so heavier, lower-resisitance cables increase the damping factor. Emotiva's DF is around 200. Various amps ranging from Adcoms to Proceed HPA's by Levinson with 600+ damping factors resulted in firmer and more accurate bass. A friend brought his $4000 Bell Canto amp using B&O's class D Ice module with damping factor over 1000. Very much liking what I heard, my research led me to purchase a Wyred4 Sound 7-channel x 500 watt (250@8ohms) version. Separating the woofers with a dedicated amp per channel not only doubled the damping factor (2000+), but kept the distortion low, avoiding an approximately 90% increase when going from 8 ohm to 4 ohm loads. The 500 watt model was chosen in lieu of the 1000 watt version due to its slightly higher damping factor, higher bandwidth and lower distortion at my typical listening level.
Achieving a high DF is often achieved with high negative feedback, resulting less transparent midrange and highs. This was especially the case with the Adcoms, which had a noticibly muddy midrange. The Levinson/Proceeds were better, but still not nearly as transparent and dynamic as the Wyred4sound which has remained connected to the M9500s for the last two years as my amplifier of choice. I was told by 3 of 3 listeners that have auditioned the $50,000 Wilson Maxx’s, that my M9500s driven by the multi-channel Wyred4sound easily outperforms them.
Contributing to this result was the addition of a Behringer DCX2496 electronic crossover modified by Cullen Circuits of Paso Robles, CA who are also the builders of Wyred4Sound amplifiers with Cullen’s design. I have periodically checked their used prices on Audiogon. They seem to hold their value as does a new Mercedes. A two-year old model sells for at least 80% of new retail. In conclusion, the Wyred4sound amplifiers would be my obvious choice, clearly in a different league in terms of quality and performance.

Many feel DF over a value of even as low as 20 or 30 is a redherring parameter.

Also, low DF allows the speaker to dampen ITSELF. When your system is off, disconnect the speaker from the amp. Pull the plug, so to speak. Thump the woofer with your finger. THAN bridge the speaker binding posts with a paper clip. yep, a simple paper clip. Thump again. BIG change, right? Well, the paperclip will simulate the amp with low ON RESISTANCE.....which is what gives a high damping factor.

You could, in the interest of science try a few other values....maybe a pair of 1ohm in parallel which would simulate a DF of about 16 on an 8 ohm speaker. This may give an idea how low or hi a DF you really need.

I think I'd like the W4S amps. They are a visual (color / finish...excepted) duplicate for my PSAudio GCC amp. Right down to panel front and back.

What is the problem with Emotiva? Well, I've never heard one. But, from strictly an engineering standpoint, they should work well. SQ? you choose. But, the difference in lifetime and build quality may be an issue in a few years. To take the extreme example, Bryston has a no-prisoners attitude with a price and warranty to match.

Magfan, You are right about stopping speaker motion by shorting with a paper clip (high DF). Pushing the speaker cone out of its magnetic center creates potential energy, and with an open circuit, the speaker will oscillate a few cycles and stop by itself. Shorting with a paper clip stops the motion abruptly, as would a high DF amplifier. Details in Bass Guitar notes, for example, are obscured by extra cone motion if the DF is low because it keeps moving when the source signal has stopped. The heavy JBL woofers I described failed to produce the sharp crackle of a lightning strike until I kept increasing the DF of the amplifiers. My testing and listening with several amplifiers with varying DF's led me to my conclusions. For example, when I connected a $6000 Classe CA-2200 to woofer section, It took only a minute of listening to know it was the wrong amplifier and I disconnected it. When I connected it instead to the compression drivers crossed over above 650hz, the highs sparkled with crystalline delight! Classe didn't state a DF in their specs. Some research told me that their DF was slighly less than 100. Their amps use next to zero negative feedback, making for wonderful mids and highs. The tradoff is lack of woofer control. If you have speakers with separate terminals and jumpers, you can remove the jumpers and use separate high DF amps for the woofers and another amp such as the Classe for the mids and highs. Believe me, I have done it and in every case, there was a noticable improvement.

Thanks for reply, Fmk.

One additional factor to consider. Yep, hi mass cones are a potential problem, but I think that speaker 'Q' is part of the answer.
A system with hi 'Q' will have plenty of overhang and maybe even a midbass peak and bloat. A critically damped system of 'Q'=.7 will produce good bass, maybe even with a low DF amp.
NFB? maybe the '3rd rail' of hi fidelity.

wyred for sound has the typical nice ice sound but holloow I owned a st 500 for several months could not take it anymore bought a modwright 100st then went to the emotiva
xpa-1 mono blocks give em 250 hours runin and they are very good on Bass I have mig maggi 3.6 and to get good bass out of them you have to have control .I also have wilson sophia 2 and they sound excellent for $2k
it will beat most $6k amplifiers in the magazines.