I buy from tower hobbies when the carry what i need, I wouldnt go much over 1000 mah though, because the more capacity the more they weigh, and foamies tend not to handle the weight on landings, also they will start getting sluggish. I use two of the 640mah and a polycharge(i charge them at the 1000 level which appearently isnt the righ tthing to do, but i havent had problems yet and its gets charged quicker) and I prolly make 2-4 flights a day. As for brand, I'd stay with the electrifly packs due to the seperate charge and discharge plugs will work with what you have now(as in no plug change on the charger). most of the larger packs due however use bigger discharge plugs so you would need to order a set of the small two pin micro plugs for the new packs, so they match the battery. deans makes the plugs and tower carries them as well. youd prolly be alright with a 1050 maybe even a 1200, but at some point all it gets you is more motor strain and slugish performance. My preferance is to stick with light packs 640-900 or so mah and just have a couple around. and if i get some more packs I will aslo prolly look into a polycharge 4, dunno if you have seen that, charges four packs at once, and all 4 packs can have seperate charge rates, cell counts, in case you have a variety of packs.