I have a dwindling stash of GP4000S in 25mm... they can be hard to find, so I order in bulk from ribble or wiggle or pbk or whomever has free shipping and good prices.

I think I'm going to switch back to Michelin Pro4 though. Pro3 cut on me all the time and the GP4000S are no better (but they both ride really well), maybe even worse than those frail Pro3 tires. I hear the Pro4 are better... more like the Pro2, so those are next up.

I've never tried the Lithions though.