James has mentioned the 7B3 have 'more capacitors' for the power supply, meaning the 7B3 will carry a heavy load LONGER while playing loud... than the same 14B3.. so the 7B3 power supplies are a bit beefier than the 14B3.. for what little it is worth. I still would say the differences would not be woth the money spent swapping. Still say go for the 28B3 and THOSE would be a real upgrade you could really hear. !!!!
As for the 90+dB.. not my problem. Yes if asked I would say it is probably louder than what is safe. But not my ears, not my problem.
I was luckier and had a 30 year job in a very quiet place. No noise at all. Where I live is quiet too... Apartment, but the neighbors are making no noise... (and I try hard to not bother them either)