Quicksilver mono amp

I would opt for the 8417, keeping in mind, however, that the tubes are hard to find NOS anymore so, whenever you do find them listed, grab them!
The mids & upper mids are exquisite.

They say the 8417 is one of the best sounding tubes....  however they are no longer in production and hard to find NOS.    That said I would choose the Silver Monos.   KT 88 are plentiful and in production still and readily available.   I have a pair of Mid Monos and they are great amps...

The 8417 went out of production due to problems with the internal spacing of the grid-to-screen grid. Too many failures! Stick to the KT88/6550!

I read the above years ago in a technical report on the 8417. I was researching the suitability of various power tubes for triode connection.