What are my Lipo options- which voltage and what charger?

if you have the vxl set-up the max voltage you can use is a 3s lipo, or 11.1 volts. for a charger anything that can handle the voltage and capacity will be fine. Also look at getting a balancer,some chargers do have balancers built in.

Mines the XL-5. I believe that 8.4 volts is the max.

So you'll have to stick with a 2-cell lipo. But the XL-5 does not have lipo cut-off, you'll have to purchase a seperate lipo cut-off unit, like the novak smart-stop, or similar product to safely run lipo batteries.

From what I've gathered I'm probably best to stick with NIHM cost wise.

otherwise if you go to www.hobbycity.com they have a 4000mah lipo for $40 which ain't too bad, and the lipo cut-offs are only about $20-$30