Triangle Stratos 260 speaker cables interconnects

I have Triangle Stratos 260 speakers that need more help.

The system is Jolida 100A CD (stage 1 Underwood mod) with an unmodded Jolida 550 amp, Cogan Hall interconnects and MIT 750 Music Hose speaker cable. A Quad L series sub completes the setup. The speakers are 4' from the back and side walls, 6' apart, and toed in 4-8 degrees.

My room is 11x14 w/7' ceilings, wood and plaster walls, and two windows with scrim curtains and carpeted wood floor, and basically untreated. There are two mirrors, one above and behind the speakers, and one on the side wall by the right channel speaker. Both speakers are strapped to industrial cinder blocks that are tilted up on tiptoes.
I've just replaced Jolida's proprietary tubes with Sylvania black plate 12AX7s, and black plate RCA 12AT7WAs. The sound stage is very wide, the listening is musical and involving, but the upper midrange is virtually not there and the highs are still tizzy, almost shrill on poor recordings.

What interconnects and/or speaker cables would be warm and liquid? There is wonderful information from these speakers; if I can tame it, my listening could be quite sublime.

I have an Audio Alchemy CD player. Would that be a worthy substitution to tame the top? Using the professional DAT...

Thanks in advance for any suggestions you might be able to provide. David