I've bought three twins in various stages of disrepair in the last year (disclaimer: have one for sale). They are a great value and under priced right now because of size and volume. They are the easiest and cheapest way to get where you're headed.
Things to look out for... late and post '76 twins have the ultralinear transformers which are not what Jerry was using and present some problems in blackfacing. I've read posts here that claim some have figured out how to make them work, but I've personally never hear done.
The master volumes post late '72 are awful, but changing them to a post phase inverter master (PPIMV) is not difficult. Also the pull boost on the later models can be resolved by not using it or removal.
At that price, if you're looking at an early 70's twin, and the jbl's are good, you've got a solid deal. If they are K120 or D120 and haven't been re-cede... even better. Best of luck.