Round neck I'd go with Regal or (believe it or not) Fender. Square neck, the ones I've seen the most consistancy from are Regal and Flinthill. If you are serious about the $500 to $700 range and are interested in a square neck then you absolutely should check with Paul Beard
www.beardguitars.com I haven't checked his site in the past year but he used to sell a Flinthill with all the goodies including new cone, nut and saddle inserts for about $600 plus he would give you a full money credit on one of his custom guitars if you decided to upgrade in the future. If he is still offering that then I would RUN not walk to him. Paul also sells THE video on resonator setup. It is an absolute must if you want to be a serious resonator player. I have two resos, a Fender and a DeNeve custom, and I love them.