I have to say you sound like me! I play flatwound P basses (foam under the bridge anyone?) and love all things retro, country, Americana etc. I too had the hesitations about Orange Terror but have taken the plunge. I'm not a big "Rock" guy and I'm happy to report that these do retro very well. I know you can get the rock sound but with your bass this amp really lets the bass do the talking. So if your bass is set up with flats etc, you'll get that vintage P thump and it won't suddenly make you Emo! Danko? Carol Kaye? These are absolutely my reference points too
Away from that though Ampeg are great, so are those tweed Fender Bassman combos. I also have a vintage 1978 Fender Bassman head but to be honest the lightweight Orange Terror head is getting more use at the moment.