Personally, I like acrylic lacquers over urethanes. 2K clears often have a very strange, uber-glossy toy-like look to them.
Acrylic lacquers are take some attention to apply, as they dry by solvent outgassing, instead of cure by catalyzing. This means that it must be applied slowly, and a buildup of several light coats as an initial barrier is crucial. Do it right and you'll have no trouble. Apply it wrong (wet and heavy) and the solvents will eat decals, and even the paint it's applied over. This is particularly noticeable on metallic/pearl finishes.
I use it over PPG lacquers, Tamiya lacquers, and Zero paints. I've never had trouble with it, and it looks spectacular applied properly.
The clear I use is PPG 468, and the reducer I use is PPG DTL 105. The clear is mixed for full scale application, and it works best through an airbrush thinned about 1:4- which makes for terrific economy. You can get both
here (although I haven't tried ordering from them yet), or at any decent auto paint distributor. PPG's website has a dealer locater.