All large JBL's would benefit from raising them few inches off the floor.I found 2X2 hardwood bars works better than spikes. If it's on carpet then you may want to place a slab underneeth wood bar and speakers. I use granite but other stone slab will work as well. this method will clear up muddy bass and get rid off tubey sound. If JBL came with a bottom base, you want to remove them before applying wood bar. It doesn't need to be too tall, it is room dependend. More bass reflection higher the speaker need to be set up.
L300 use LE85 vs Olympus 375, the main difference is in the midrange. 375 has silky velvet texture vs LE85's clean sound when driving them both with triod amp. And price do reflect the prefference. But L300 is easier to get a satisfying result. Or should I say L300 is more balance(better crossover network design?) than Olympus. In my system I use 3 way electronic crossover instead of the original. Finding the balance between current hungry woofer and efficient compression driver is the key to good sound.