how much do cheap cells hinder performance

[stampy]

I posted a while back on urc forums about the horrible performance i was getting with my 7018 and my chili pepper motor (540 4400kv) on 6 cheap $20 3000 cells in my rs4 mt. at first i though it was the motor cause ive never seen any body run this motor in a truck. but when i posted that every body said it was the cells. with that setup i was getting to maby 25mph geared 68 14 32p i think it was about a 12to1 ratio. at around 14to1 (98 18 48p) it wouldn't even try to get the front tires off the ground, to say the leased i was steaming mad that this 200 dollar bl setup wasn't performing like i though it would. my old xxt i bought from a friend with a brushed 9t and a cheap $15 2000 pack was it seamed like 4 times the power of my bl setup on about the same quality of cells what gives. i know now that good cells are a must but how much performance is a person going to see going from cheap arse cells to say some nice gp3700 or ib3800 or even lipo? take my case for an example, how much could i have gained going to nice cells?