Hey there, bbj! I definitely agree with Tony and Matthias. As for the "C" rating, go as high as you can afford (as Tony said) but you can surely stay away from the 50C+ packs (as Matthias said). I say that you can stay away from the higher "C" ratings for two reasons...just as Matthias said, some of the manufacturer's aren't post a "true" C rating and still charging more money for the same packs. You can also stay away from the higher "C" rating packs because you said that you aren't doing any 3D flying right now. I imagine you are going to be doing beginner stuff, sport and/or scale flying. That being said, because you aren't going to be putting a high demand on your packs, anything from a 30-45C pack will suit your flying very well and they should last quite a long time (provided that you take care of them). I surely won't go less than 30C because, when I was first flying just beginner stuff with mild sport flying, I puffed a 20C pack pretty badly. I bought the 20C packs because they were cheap and I wanted to fly. I just didn't know any better. Now that I've got a bit more experience under my belt, I don't have a single pack that is less than 30C. Most are 35 or 45C and they are still quite solid and square, as if "almost" new.
As for the brand to use, again, this is just based on my experience...I do have some of the Blue Turnigy packs for my 500. I've had them for almost 2 years and they are showing very slight signs of puffing. Mild swelling, at best. I have some of the purple Nano Techs for my 450 Pro DFC and they are very solid with no signs of puffing or swelling. I have some Gens Ace and Glaciers for my 600 Pro DFC and they are also still very solid with no signs of puffing or swelling.
Mostly I am a sport flyer. Last year was my first year's experience with any 3D maneuvers so I am starting to, not only push myself but also, pushing my helicopters and batteries.
In the end, the batteries to buy are going to be based on what you can afford and then what experiences you have with each pack. Pulse and Thunder Power are two of the big names that I know of. A lot of pro's use them. I will be getting more of the Glacier packs because the distributor is relatively close, their customer service is awesome, and I'm quite happy with the packs that I have.
Good luck!!