+1 for HD500 + JTV combination

The VDI interface allows the HD500 to control the JTV, so change a patch by pressing a pedal and you change the variax model (including the tunings) and you can also turn the variax controls into extra expression controls on the HD500.  You can take both variax model and magnetic pickups as feeds into the dual paths on the HD500, so you can have acoustic and electric sounds at the same time and cross fade between them.... etc, etc. 

The rig is really small and light - the JTV via VDI into HD500 then XLR to PA.  A small FRFR powered speaker (I use FBT MaxX but there are loads of other options) covers monitoring and can be fed from the other XLR on the HD500. You could of course use your Acoustic Amp as a monitor.

I have HD500 and JTV69 + the monitor and I think it works great with loads of flexibility; it is also a single trip to and from the car; is assembled in a minute and gives the same sound pretty much all the time (acoustics of location dependent obviously).  But that same flexibility plus point is also a big problem for some - you have a large number of virtual guitars, and reasonably large number of amp options and a hundred or so effects all of which have been modelled down to the smallest degree of response (including overloading the inputs). That makes the apparently simple rig very complicated indeed - and it takes quite a lot of time to really understand how it all works; and it isn't necessarily that obvious.

There are loads of example videos on the web that show JTV and HD500 combinations workinig together - some are even not just metal sounds!  Look at a few of those - especially the Line 6 official ones or ones from respected people (try the Andertons ones - it is a music shop in Guildford but they do some quite detailed video reviews that helped convince me). 

Now comes the practical problem - to understand what it can do and to make sure that it has the right "feel" you really have to try it as the full combination; just 'cause I say it is great just means that it works for me but it doesn't mean that it will work for you.  The perfect answer is to find an existing user who you can spend a few hours with, but you need to find one first; I would be a candidate, but I live south of Birmingham (UK).  A very important factor is that (as usual) the demo patches on the HD are rather effect heavy and when trying the combinations you really want to start with a blank rig and slowly add components testing as you go - if you go into a Store and don't know how to drive the HD500 you may well be disappointed, but if you can work out how to get a blank patch and then add just an Amp you will get a better idea of how good the combination can be .

Finding a guitar store that has both components actually on display can also be tricky - even harder to find a store where the assistant has a clue about how to put them together and get the right settings. Fortunately Manchester has more options that some, but make sure you phone first as website stock isn't necessarily in store (I wasted my first trial of a JTV because they only had a HD400 and the battery was flat so the JTV couldn't be powered up ).