Belles 21A upgrade

what is the upgrade?

Mundorf M-caps gold of V-caps TFTN's. I'm not sure what it
means but here the specs are better than Auricaps and exceed their sound quality

I had a 21A on loan for an audition and it was the stock unit. I don't remember what the stock output coupling caps were. But definitely remember seeing several Orange drops. I advice replacing those caps as well. They tend to blunt the transients, especially the trailing end. Also, I'm sure you have rolled the tubes?

I haven't rolled the tubes yet since I hear the unit comes with Mullards. Which tubes are better 5814A or 12AU7? Any recommendations for the system listed below will be welcomed:

21A Belles tube Pre
Belles 150A Ref
Rega Apollo
MI2 Biwire Goertz
AQ Columbia IC
Vandersteen 2 Ce Sig II

Thanks,
Wig

the mullards were too rolled off at the extremes for me.
the tubes i like best are raytheon 5814a(great),raytheon 12au7(great),
brimar 13d5(great), cbs/hytron 5814wa(great), rca 5814.
for a smoother sound any of the conn or baldwin organ 12au7.