Re: Your ears on Rio Grande P-90's?
I had some, and they sound pretty good, but hot. Unlike most P-90s, they sound a lot better on an amp that has some headroom, like a Twin Reverb or a 50-Watt Marshall. Less good on amps you'd think of as classic P-90 amps like Fender Deluxes. A little bit darker and grimier than most P-90s, but they still have great shimmering highs on an amp that they agree with. Depending on your application (solid body, big amp) they could work for you.
I think a more vintage P-90 might be more versatile.