Yes, I agree.
If you can find an early silverface Fender amp with no master volume (which is about 1967 until ... ?) it's going to be a lot cheaper than the virtually identical blackface model.
Princeton is a good way to go, but you would have to mike it for a regular gig volume.
Of course, your 'lower volume' may require no micing.
As for the various new 'old' Gibson guitars - I have very little experience with the new or re-issued guitars. I have heard that Gibson are making really good guitars, but as always, the guitar that says to you 'Take me home, I'm yours' could have come of the assembly line one away from one which you think absolutely sucks, so you just have to keep playing them until you find 'the one'.
P-90s are excellent pickups, 'if that's the sound you want' They are great for classic electric blues - but how the newer ones sound compared to the early sixties ones, I've no idea.
You might want to shop around and find some original '60s ones if you're really serious.
Godd luck,
foo