Thanks for answering.
My speakers are the Q Acustics Concept 500 and eventhough they are not super efficient (90 dB), the 2x48 wpc of the LM-508 drive them very well. It has dinamics, tone, layering, bass, sweetness, everything. But as always, I guess we wouldnt be audiophiles if we weren't always looking for better sound.
By the way. I already have a pair of active subs with their own 500w class D amp.
I think you @oldhvymec nailed it. I would like to see how the LM-508 could sound if I relieve it from handling the lower notes, like 200/300 hz and below.
I guess I could also use a crossover to split the signal between the speakers and the subs (not biamping), but I guess the subs can only sound good up to 80/100 hz top, if not less.
So, to really relief the valve amp and release it's full potential, I guess I have to go biamping.
The big question is if it's worthwile the effort and time. So maybe hearing some other similar experiences could encourage me :-)