I think the issue with flattops is that they have poor projection. They sound great up close, but just don't carry and cut.
Freddie Green managed to cut through the band just find with his Stromberg.
On my archtop journey I found out that Loar (chinese made) archtops seem to be REALLY loud as well as reasonably priced.
It's obviously nothing like a vintage Gibson or any other archtops of that sort, but they're affordable and LOUD.
http://www.musiciansfriend.com/guitars/the-loar-lh-300-archtop-acoustic-guitar
That'll do blues, country and bluegrass, but is probably better for jazz.
Resonators are probably more what you want, but I know the Loars are loud, so I thought I'd add my 2 cents.