I would not buy either a Singer or a Bernette. Perhaps take the ones you have to a different technician.
If you want a new machine, find some dealerships in your area and go in and actually sew on the machines. Dealerships often have very good used machines that they have taken for trade-in, so that may be the way to go.
In terms of brands, a lot depends on your price range. It sounds as if real Pfaff and Bernina machines are outside your range, so I would be trying out Janome and Brother machines. If Sears is still selling Kenmores (which are made by Janome), try out those too. (Sears is phasing out their machines.) Machines are usually *very* difficult to return for refund (although sometimes dealers will allow you to exchange upwards), so I would not purchase a machine before actually trying it out.