Have you had a chance to run different manufacturer's units?
If not, I highly recommend attending a LDMA GPAA Common Outing so that you try out about every piece and type of high banker out there.
We ran Keene, Proline, Gold Hog and Martin units.
Each one has it's pros and cons. For the most part, pick one and you will be happy. Setting it up the right way will yield more treasures regardless of which one you pick.
I bought one last year (2.5 Keene Combo) from Crissions Gold Mine in Dahlonega, GA. I am very happy with the unit, though, like most, a rain suit is recommended, lol!
Crissons also stands behind thier product. They carry Keene, Gold Hog, and maybe Proline. Martin Prospecting (Inman, SC) carries the Martin line..and Todd Martin is one of nicest most helpful people you can meet and also stands behind his product.