For modeling, there is also the SPICE-based computer stuff like
Peavey ReValver. I don't think it's all that expensive, although you'd need a preamp interface of some sort I believe. The fidelity is really good for this type of modeling since it recreates each stage of a tube amp with analog component modeling (different than POD technology), and then the impulse responses for the cabinets are very good. I think there are some free ones also, but I can't remember their names. Maybe I can dig them up later.
Edit: Found the bookmark I had saved. I will just link
this post that has a lot of good info. The specific one I was thinking of was
SimulAnalog which has a signal path accurate clone of a JCM900.
Last edited by RonMexico; 02-08-2013 at 05:28 PM.
Reason: Links added.