Have you tried Versafine, Rachel? That's what I use about 95% of the time. I use Winsor & Newton 140lb rough Artists' Watercolour paper, but I usually use the wrong side since it's a bit smoother, and even with detailed stamps I rarely have trouble with a clear impression. Onyx Black, I think the black one is called.
I'm not a fan of Memento - I have it in case I need to stamp a few images for Copic users, but I don't think it's a true black.
And I scored some Hot Press Daler Rowney the other day - still got to try that out but it's certainly super-smooth. I think somebody mentioned it on another thread