Need Some Educated Advice...For a Newbie Tuber

Here's my simple system: Jolida 1000 w/stock tubes; Ah Njoe Toeb 4000 CD, upgraded; Infinity Kappa 8.1 (in perfect condition...owned them for years).

I love the overall sound of this system...my first tube equipment. Had Adcom 555 and Nak OM7 forever and ran them through my Infinity's....sounded ok, but just lots of power without finesse. Now, I'm hearing sweetness and ripe midranges with instrument sounds and staging that I never heard before on my discs. Bass is pretty adequate and soft and natural. Highs (vocals and full string sections playing forte) sometimes sound muddy and shrill...single instruments -- violin, guitar, brass, etc. are pretty clean al the way up.
Not sure where I could/should tweak or change to improve. Comments on system and advice would be most appreciated.