Suggestions for an integrated upgrade please

You might consider these 5 - 

Marantz PM10S1 (Refurb) $4,999 200/400 w/Ch, all analog, 2-Balanced in

Luxman 505 UXII $4995 100W/Ch all analog, 1 set Bal inputs

Cary Audio SLI-80HS $4995 80 W/Ch, no Phono

McIntosh MA-252 Hybrid $3495   100/160W/Ch, 1 set Bal, Phono, Sub Out

Mark Levison 5805  (B-Stock) $6495 125/250 W/Ch Digital/MQA/Phono Stereophile Class A

2 Japanese, 3 American; 3 Solid-state, 1 Tube, 1 Hybrid, Technology wise, this covers the scope. I would hold out for the Mark Levinson myself, or go with the McIntosh because it is not only competent, it is sculpture. The high-end Marantz amps don't get much coverage in the US, but when they do, people are shocked at how good they are. The Luxman is also very, very good, and has lots of flexibility. Cary is a veteran tube amp shop, and they don't often put a foot wrong.Switchable beween Triode and Ultralinear modes might be enlightening.

Any Musical Fidelity in your price range.

Kinki Audio INT EX-M1 $2,395 215wpc @ 8ohms , Class A/B,3 year Warranty. China

kinki-studio.com/ex-m1

Exposure 3510 INT 110wpc @ 8ohm Class A/B $3,000 3 year Warranty. UK

exposurehifi.com/portfolio-items/3510-series

You're getting excellent suggestions on the integrated amps.

Once you figure that out. Here are some additional suggestions:

1) as mentioned the 87db speakers may be veiling some of the timbre and detail. Think about getting something  in the 91db+ range.

2) flac files are still compressed files. Try to transition to full-size wav files. Storage is cheap these days. If you use iTunes, set it so it doesn't 'manage'  your files. For some reason iTunes kept making my wav files lossless so I had to transition off iTunes for my music. They sound much better for it.

SUGDEN