@steverrino, perhaps the Luxman and your speakers are not an ideal marriage but you should not be hearing what you describe. We know nothing about your room acoustics nor the shape, size or structure. Cables and different amps at this stage will not achieve much, not if your listening position places you in a partial null of which there are many in all untreated rooms.
It is difficult to conceptualise the damage strong early reflections cause, something that can not be solved with EQ
A smart suggestion offered by a poster above is to consider subs, an excellent way of taming peaks and nulls whilst also bringing lots extra to the party. An improvement is gained across the spectrum.
I've heard Devore 0/96 driven by a 300B single ended amp sounding delightful.