Upgrade suggestions from BAT VK-300xSE

I'm a 300X-SE user who formerly owned an ARC VT100 Mk-I &
Mk-III.
I'm my circumstances (smaller room, lower volume listening) I much prefer the BAT to the ARC.
The tubes generally sound "polite" and homogenized -lacking in color and texture.
I swapped out the ARC for some borrowed BEL 1001 Mk-V monos ($8000 pr.) and was stunned by the improvement!
I guess I'm just a solid-state guy at heart.

The last time I checked, a VT-100 factory retube (power tubes only) from a dealer costs $850.
This is every two years if amp used daily (1-2 hours) and weekends (4-6 hours).
You can use non-factory tubes, which go for around $400,
and bias yourself.
This is partly why I switched to SS.