Yep - the 4600 packs pack more punch for stock. I race stock (not very well...) and always use an EP4600 or IB4600 for the mains.

I'm afraid I have no A123 packs to test. If I had one I would be happy to test. I'd like to also compare some high-end LiPo packs to see how they measure up but don't want to blow a bunch of cash just for that.

For my own use, I test everything at 35 amps but for packs I am selling I hate to push it so stick with 30 amps - I just do a cycle to make sure the packs are performing properly before selling.