Panasonic is supposedly quietly getting out of the RC battery business. This http://www.rczone.net/modules.php?na...rticle&sid=269
is about the only thing really published on that and it's old but the Panasonics are definitely getting hard to find.
I'd go with the Sanyo 3000HV's as the best of what's currently available for stock. You can hammer them at 8amps and they like it to make up for whatever other deficiency they may have. In my opinion, the GP’s would have to be significantly more powerful to make up for the added weight in stock and I just don’t see that yet.
As OVA said, I'd go look at ProMatch. I just ordered a couple of their packs a month ago and have been very pleased so far.