Matt, I am by no means an expert on this. Journeyman, at best. As such, the best advice I can give you would be to speak with a knowledgeable stereo shop owner who knows what s/he is talking about and/or with some technicians at on-line sellers like Crutchfield, Music Direct, Audio Advisor, World Wide Stereo, Audio Advice, etc. That being said, personally, I have found that 4 ohm and 6 ohm nominal load designed speakers tend to perform best when they are fed high current from a good amp. High current does not necessarily equate to high watts of power. I think your amp would do better with 8 ohm nominal load speakers. Good Luck!

Matt, From your list of equipment, there should not be any anomaly with the sound, assuming everything is installed properly. I assume that your cartridge is likely a magnetic one and the amplifier's phono input accepts magnetic cartridges. The speakers may be the issue (https://www.tonepublications.com/old-school/martinlogan-aerius-i-loudspeaker/). Those are good speakers, so I would have thought it's not the issue.

If you could provide a bit more information on what tests you may have performed, any more detail on what it sounds like, or anything you have noticed since your post.