I agree with the other posters, that the UA610 isn't as great on guitar as it is on bass, and that a mic preamp can never substitute for an actual guitar amp that has speakers and room sound.
Still, you can get some warmth with a tube DI that is nice for the guitar signal. I have had great results with an Avalon 737, and also a TAB v71, and then using plug-ins. I would NOT try to get guitar distortion out of a mic pre. That could go really badly.
If it is a guitar-based project, and you are getting really serious, at some point you are probably going to want to mic an amp, of course. Still, I have gotten some pretty sweet DI sounds, just adding plugs, IMHO.