It doesnt have to be all that expensive. Personally my favorite batteries right now are the unmatched SMC IB4200's. Tons of power and at an amazingly low price. They come as stick packs, so I just cut the shrink wrap off, rip them apart, dremel off the little bits left on the ends from the welded on tabs, then assemble just as you would any matched pack. Get a Dean's battery building jig, and the Novak smart tray is one I use, it is very simple to use and works great. Just equalize the packs down to 0.9V per cell after you race then put about 1000mah in them if you are going to race again next week and they are good to go. IMO there is no need for matched packs unless your running in a ultra competitive stock class, for mod you can easily make run time with less than 3000mah, and its offroad so of course power is rarely ever an issue. To tell you the truth the IB3600 stick packs from SMC do just as well as the 4200's, and they are insanely cheap. 90% of the guys at my local track run 3600's.