I think there's a couple of us on here that use modelers as practice. I've been curious about a few things. 1) Do you dial up a tone that's exactly like your main amp? 2) Or do you get something that's close enough? 3) And then do you use the head your "emulating" to reamp your track? These questions is also applies to the ones that use modelers for scratch tracks when you are recording. Right now I've got a Formula Pre for my tones when I do my recording. When I get back to the states I plan on getting an amp (not sure if it'll be a V or Roadster/Triple) and like to hear as many thoughts on this as possible.
Modelers have the great advantage of being very quiet, so they're nice for practicing in an apartment, or around roommates who are sleeping/studying/etc. That said, most amps can be dialed in to have a somewhat OK tone at low volume levels.
My advice: get a cheap digital device for quiet places, and sink the rest of your budget into a really nice full-on amp.