I just bought a Peavy ValveKing 212 and I'm also considering buying the Epiphone sg with the tailpiece and whammy. I was going to buy a Gibson sg standard but decided to buy the amp and go with the Epiphone. If I do end up purchasing the guitar I would also be contemplating on buying some better pickups, say, a set of active EMG's or maybe even the Gibson stock pickup's for the sg. Should I spend the extra cash or leave the Epiphone stock. As of now I'm on the fence with this one because it seems like no matter what guitar I plug into this amp it sounds good.

Also, is the whammy even worth it to get? I've heard some ill feedback before about them.
Is it a bigsby? If it is, those seem to go out of tune faster than regular trems. IMO you should put some EMG's in the Epiphone. You'll get a huge difference in sound compared to the stock Gibson's.

Try it out at a GC or something like that, if your really unsure.
Is this the sort of "Bigsby" you mean

Its actually a stock Epi tailpiece, based on the Gibson "Maestro" vibrolo of the 60's