The main reason the OP has to go so deep into the volume pot is the Vincent integrated. It has an input sensitivity of 425 mV, the result being that he is going to have to probably run 75-85% full out on the volume pot to achieve higher SPL's. (I have a Shengya integrated-Shengya manufactures the Vincent product-with a 375 mV input sensitivity so I'm in a similar position).
With a similar, or even lower powered integrated with an input sensitivity of, say, 200-250 mV, he might never go past half way on the volume pot. But that does not necessarily mean that it will sound better.
While it may see a bit weird, I will reiterate what I said earlier in the thread for the OP. Turn it up, even if you're at 9 out of 10 on the volume pot, and if you can achieve the volume/SPL's you want to, don't worry about it. You will certainly not be hurting your amp-it is designed to function this way-or anything else in your system.
Go back to 60 dB and try it out even if you have to almost max the integrated out. I would bet that you will have much better sound quality.
Just be sure to turn things back down before playing a CD!