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 Maxxs, 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 Cullens 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.