Best monoblocks for Tannoy Legacy Arden

It could be at least partly due to a bright recording of Aerosmith.  Many rock recordings are a bit thin and shrill IMO. 

I'd be  more inclined to try some tube rolling or swap some cables before replacing the amps.

What amps might work best to get the best overall sound from all recordings?

Benchmark

https://benchmarkmedia.com/products/benchmark-ahb2-power-amplifier

Cut up a tshirt, I’ve said this. Many places here

cut square cotton shirt in many same size to fit over tweeter

start with one layer, then two, or 3 depending on your ears and reflection 

I do this all the time, it’s cheap d l costs you an old shirt. 
use double sided tape or some light glue at the corners of the cotton squares to hold. Together. 
I bought 3-M no residue thin Velcro trips one on top one on bottom , also to cotton squares.  Gets rid of many harsh highs   
 

or just use no residue tape for rock music. 
 

I also cut racquetballs in half as footers for components. 
Home Depot or any home store, bought a 4” solid concrete square for turntable 

also a home store, bed bath beyond etc, I bought 2 beautiful solid wood cutting blocks, which I sanded a little and stained lightly cherry wood stain. 
 

dont l fall for the gimmicks   

@knighttodd "With the right music and recording they sound fantastic.".

You may have answered your own question. Nice amps, nice Preamp. Decent tubes in stock form. Your PL EVO400s with EL34s are fairly smooth. EL34s, no?

Some early Aerosmith Columbia recordings were known to be "too bright". A common complaint. Try a Remastered version, same tracks, does it get any better?