I don't believe that the brand of cells makes that much of a difference, as I have tried both a cheap chinese 3800mAh 20C 4S & a Maxamps 6000mAh 20C 4S, back to back, & the only difference was very slightly lower on initial punch with the 3800 (due to available amps.) & run time was longer with the 6000 (obviously). Top speed was the same in a converted Revo with stock gearing & a X1-CRT with stock gearing.
So, I don't see what could've been wrong with you batts to make that much of a difference.
Either way, they're still faster than nitro!!!
that might be telling you something about the quality of Maxamps packs
#1...good luck getting a stampede over 60mph.....there just not stable enough to go that fast...the vxl on 3s will easily get you to 70+ in a rustler or bandit with the right gearing
now take that velinion motor and pair it with a mm on 4s, right gears and tires that will hold up and you will do over 80mph