The thing is, most people say when feeding your subs a high level input, they take on the sound characteristics of the main amp. This is probably true to an extent, but in my experience, the high level signal simply makes the subs sound/perform better. They become tighter, punchier, more detailed and musical. And I can honestly say, when I was still running the Polk subs, when I switched out the Schiit Aegir amps to the Roksan Caspian amp, the subs did in fact get a little bit heavier in the bass department with a bit more tightness and agility. Something these Roksan amps are known for.
Beyond that, running high level, you don't have to worry about cable length nor do you have to worry about picking up any noise or hum since the signal going through the cable is at a much higher voltage than any air-born electrical noise. And again, the cable quality isn't really all that critical. As long as it's decent quality copper cable, you're good to go. With these JL subs, they use these little plug-in screw terminals that only accept 16 gauge or smaller wire, so I'm just using cheap braided copper lamp cord from the hardware store. It works perfectly fine and still sounds 100 times better than running RCA's to the subs.
And yes, the subwoofer does block that door. I keep it closed at all time, and have it locked just for good measure. It just leads to the hallway, which you can also get to via literally two extra steps going through the kitchen (the door to the left of the left speaker. And when doing some really critical listening, I close that door as well.
I've tried it both ways with the my SL3's, NHT 2.9's, Sonus Faber Venere 1.5's, Klipsch Heresy III's, GR-Research X-Statik's, etc, etc, etc. Virtually all of the speaker I have or had, large and small, and always had best results running them fullrange and adding the subs in for fill. But that's just me.
Just curious as to why you had that 35 Hz gap between crossover points? 95 Hz for the SL3's and 60 Hz for the subs?
Wow, a 28 Hz crossover point?! That sub is barely doing anything at that point. What speakers are you running?