Run time estimations

[GorillaMaxx360]

OK guys you know of my project i am building a basher i wanted to go lipo and i wanted to go cheap. I have decided to go with the A123 batts for one reason durability and a little more tolarable, other wise if it was for racing it would be the maxx amps batts. I was browsing A123's site ans saw many different battery choices i want to go with 2 es lipo packs they sell 2 2s lipo 2300 packs with charger for 220 and two 4600mah 2 2s lipos packs and a charger for 300 what kind of runtime am i looking for with the 2300 and 4600 batteries runtime matters but is not extremely important being the 15min charge time will it be worth the extra 80bucks to dbl the runtime and what kind of time should i expect from each pack probaly going to run them non parallel (i think this means run the combined voltage and parallel means combine the mah) i want to combine the voltage so that is not parallel right. Thanks guys.