I know that this thread is older, but I stumbled onto something last night that I have not found on any dealer's websites. If you go to Holland Brooks Detectors, they have a side by side comparison tool. They are not TNET sponsers and I think you can get better prices out there with the dealers on TNET.
Personally, I would spend more and get an AT Gold or AT Pro. You get ground balance and a waterproof package and a few more things that are probably slightly less important. To me it is worth spending a few hundred more to do so, or find one used for about $500.