I'm very pleased with my Michelin SM100's, they're really good in wet conditions, I've never felt a tyre slipping or creeping anymore since I have them, it's another universe compared to the stock tyres...
I've heard lots of good things about the Bridgestone ML50 as well, it's a very soft and sticky tyre.
Be careful though, because some brand makes a good tyre, it doesn't mean their other series are good as well...
Any way : if you're concerned about wet conditions, stay away from those sporty looking semi-slicks, the kind with those arrow shaped grooves and large patches of "ungrooved" rubber. Most of these really suck when it's raining !! The same goes for offroad-style tyres on tarmac.
As for fitting larger sizes : been there, done that. Some aspects will work (more top speed, good looks) but you will lose some (or a lot of) stability. A larger tyre on a narrow rim has less stiffness sideways and will feel like you're drifting away, just like an underinflated tyre does, and by overinflating it, the surface can become rounder and higher, which feels very unstable.