BAT amp users - any fuse recommendations?

I have a BAT VK-55, OEM fuses, curious if other BAT users have experimented with after-market fuses, and if so, any recommendations?  
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I use Synergistic Research Black fuses in my Rex Monoblocks, Rex preamp and I love them.  I think they are worth the relatively modest investment.
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I put on (6) HiFi Tuning Silverstar in my BAT Vk-600se, the difference  compared to OEM fuses was apparent but not that spectacular. I talked to Victor Khomenko and he was not recommending the use of after-market fuses ...
I have a vk55,  well a pair of them, ,, what tubes are you running,  I love this amp alot.
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batman1971 - I bought my VK-55 used, it's my first tube amp, and it came with the standard output tubes, Russian 6C33C-Bs.  The driver tubes were Sylvania Chrome Domes, now I am trying Upscale Audio's "Early Russian" 6H8C/6SN7s.  Initially these did not sound too good - mids were front and center at the expense of everything else, which faded into the background.  After ~40 hours of break-in, they started to sound very similar to the Chrome Domes; after 100 hours they are very pleasing to me, mids have more resonance and highs are slightly clearer, mid bass seems to be a bit more powerful as well.  Would this be described as "more tubey?"  Open to trying others...any recommendations?  Also, I have thought of finding a second and going mono, is there a downside?  Worried about more distortion.