For sure! This is my go-to tube swap when I want to bring the gain down on an amp - and all the PRS amps I've played have plenty of it. V1 could even be a nice spot for one, but it would depend on what the effect on the clean channel would be as well, because one half of the V1 tube services on channel, and the other to the other channel. IMO, every tube amp lover should have a little stash of 5751's to play with. The nice thing about them vs a 12at7 is that spec-wise, the 5751 is more like a 12ax7, whereas the 12at7 is relatively much less like a 12ax7. Tonally as well, the 12at7 sounds much thinner and more harsh than a 5751, in the instances I've tried them. Although, I don't think it will hurt anything to use the 12at7 in an instance where the 12ax7 is stock, as the way the specs work, from what I understand, is that the 12at7 can handle more. It's the reverse that can wear down a 12ax7 faster - I read it on the internet, so it must be true. In the spirit of modding something, I suppose if the 12at7 gives you what you want, and it's not hurting anything, by all means, do it. But I still recommend trying the 5751 in those instances as well, just to see what the differences are.
Also, while we're on the topic of the MT15 tube chart, I just want to say how brilliant it is that PRS designed an amp that uses all 12ax7's for the preamp, from a maintenance and gigging point of view. You can just have a few extra 12ax7's and a pair of 6L6's on hand, and if anything takes a crap, you don't have to worry about having a whole selection of tubes on hand. Very convenient. It would be extra nifty if they would add some kind of quick access door to the tubes, to make changes speedy. That and the external bias check would truly make the PRS amps a maintenance and gigging dream.
