Not trying to be negative here either (like other posters have also mentioned), but I sometimes wonder where ARC come up with these designs???
There has been a lot of negativity towards ARC for years on this Board, long before it's recent troubles, and as an ARC fan I have little trouble ignoring the naysayers. All that said, on this I agree. I bought my first ARC amp, a VS110 from what I gathered was a very wealthy and knowledgeable guy who had a collection of ARC amps. Years later after buying the VS110 from him I contacted him to say hello and he mentioned he had another ARC amp to sell. I lost the email and can't remember the model name/number but what I will never forget is looking it up and it looked like a welding machine. It was similarly vertical to the Ref 750 but far more industrial looking. Those of us that follow ARC closely recall some real duds, regardless of looks, in the VT range. They were almost universally panned sound-wise. They also were very difficult to bias without being an expert.
I do wish ARC would not mount tube sockets directly to circuit boards. The implementation, finally, of fuses on the tubes as in my Ref 80S is welcome.
VAC and others have built and sold monster tube amps with vertical designs but power is useless without reliability and user-serviceability.