F4 Amp Upgrade? Best "300B-like" Line Stage?

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I have a stock First Watt F4 amp that I may want to use for driving my forthcoming ~ 94db speakers. Presumably by now, there have been quite a few basic mods done on this amp.

But what are those which most listeners found made the biggest improvements to the F4's clean but tube like sound quality?

My other goal is choosing a line stage for maximizing the chance for the F4 to sound like the best 300B amps. http://www.airtight-anm.com/components/atm300.html

In the F4 manual, Nelson Pass said that he had no problem powering his 94db speakers in his 11K cu ft room with 5 volts driving the F4. As my room is only 2300 cu ft what tube amp line stage will help me achieve the best 300B-like sound from the F4?

OR, should I forget the whole thing and pursue a V-FET amp??
 
If you have the amp you want your F4 to sound like. Why not just use it rather than make your F4 try and mimmic it. It will probably never sound like it because it isn’t it. Each one has its own sonic signature. Maybe put them on an A/B switch and alternate. Everything down to how much wax is in your ear canals today: to what mood you are in can completely change what either amp sounds like.

Ears, amps, preamps and at the top of the list rooms are all different and subjective. Use whatever makes you happy!
 
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Again, my speakers will be ~ 94db/w/m in my 2880 cu ft room ; 11 ft triangular ceiling. While the room may not be considered big by Earl Geddes standards the speakers would likely need 5 wpc or so. That line stage doesn't appear to be able to deliver at least 7 volts for driving F4 to prevent excessive distortion and prevent risks from hazardous transients that could vaporize my drivers. That looks like what might happen with this line stage, though it's twice my budget anyway.
https://www.manley.com/hifi/neo3br

Alternately, which might be among the best tube-based commercially built line stages to drive the F4 for my speakers-but which can make the F4 sound the most like a 300B SET amp-even if it didn't use 300B tubes?