Totem Forest Speakers.....

See if you can borrow a better source component (a Benchmark DAC-1 perhaps?) before driving yourself crazy with speaker placement. I know speaker placement is very important, but you have very high resolution electronics, speaker cables, and speakers, and a CD player that's not in the same league. Maybe the Krell/Kimber/Forest signal chain is revealing the Yamaha's shortcomings.

Your room and placement is asking for trouble--same resonating frequency for all four walls, half the wall length for the space between the speakers, and 1/4 the wall length for the space between each speaker and its wall.

You're suffering from garbage in, garbage out.
Great amp and speakers!

Matt, synergy is so so elusive. I'm still trying to capture it in my system. Source amp speaker synergy is complex or can be simple if you know of system(s) that work well and replicate that system. The Yamaha appears to be the lesser component in your system. If I were you I would look at the source first and replace it. If you then do not get what you are listening for then look at the 400xi and replace it.

A square box is the worst scenario for acoustics. The Krell sounds average to bad with the stock power cord and run un-balanced. You shoul run it balanced with a musical CDP and a great PC and interconnect like MIT offers. If you want good advice from a veteran in the business call Joe Abrams at Equus Audio (Portal Audio). He will cut through the "well intentioned advice" you are getting and give you some solid options to pursue:O)

I would definitely change the amp; it is not a particularly "musical" component. Contrary to other posts, IMO it is much too analytical and clinical for your speakers.

I would also look at the cd player, speaker placement, and room treatments as well.