Li-Po or NiMH? I'm confused.

[rcjmaxx]

I have a lipo setup I'd like to get your opinions on.I have an Emaxx with the 9L/9918 combo,with 14 3300 cells installed,a steel rolecage and stock tires the truck weighs 10 lbs 2 ounces.As a basher I run 15/65 gears,for top speed I run 18/65.I love the performance I get with this setup but want more runtime.I'm looking to go with 2 PolyQuest 4400 3s lipo packs in parallel,what can I expect in runtime and performance?Would 3500 4s be a better way to go?My charger can charge up to 3 lipo cells.I run 40 mph with no problem,will I be able to exceed this by much? Thanks