Hey, Just thought I'd throw in my opinion.
I think the sanyo's are great cells. I have both the GP's and Sanyo's The GP's tend to stay cooler than the sanyo's. Lower resistance overall, longer run times and cheaper to boot!
You can't go wrong either way. Panasonics are good cells too! It's just that the GP's are relatively new comers but have set quite an impression on most folks.
I ordered my batteries from Promatchracing.com. I originally ordered the sanyo's 3300 cause they were on sale. They had sent me the wrong cells so I decided to try them out and boy was I happy. I got the Team Spec cells.. Not really racing but good quality cells right from the beginning make for a better choice.
As for whether or not you should go to 3300's. My recommendation is SURE! why not? your going to buy cells anyways and you might as well get some good ones so you don't have to upgrade like the guys with 3000's will later. Since you're learning to drive I really really recommend the 3300's they last a lot longer than 3000's.
The Sanyo 3000's I have typically run for about 10-15 min medium throttle. I've used these packs for about 7 months and they still hold 3000 mah according to the integy 16x7.
The GP 3300's will last 20 - 25 min same amount of throttle.. and that's on the very first charge! These GP's hold about 3600 mah on the very first charge..
I don't know about the Panasonics but the other two mentions are top quality also. You should give it some thought. GP's are about $45 a pack for 1.13+ 385+ @ 30 amp discharge from promatch. Which I think is damn cheap compared to most other brands.
Anyways, whatever decision you make you'll have tons of fun driving the car.
I hope this helps and I hope I didn't give you pointless information considering I didn't mention anything about the Panasonics.