ill try to give you a crash course in lipos!

MAH is runtime, or capacity.

"C" is the discharge rate. the higher this number, the more "punch" the lipo can put out. for 1/10 scale rc's, you want 20c or higher.

now, the MAH and "C" work together. a 20c 3000mah lipo will not give the same runtime as a 30c 3000mah lipo. why? the "C" rating is how much punch the lipo can put out. the more it can put out, the less draw on the battery. thus, slightly longer runtimes.

2s lipo is 7.4v. each cell has a nominal voltage of 3.7volts. the cells cannot be drained below 3.0v. that is why the ESC's have a LVC(low voltage cuttoff)
it will cut power to the motor when it detects the lipo's voltage to be 6.2-6.4volts total.

a 3s lipo is 11.1v.

lipo charger also "balance charge" meaning they make sure at the end of charging that both cells have the same voltage.
when a lipo is finished charging, each cell should have 4.1-4.2 volts.


now, lipos dont slowly drop in voltage like nimh packs do. as you run a nimh pack, you will notice less power, untill the battery is almost drained and it takes a huge drop in power.
with lipos, you get almost the same power from beginning of run, until the end with the LVC cuts power.

for the caldera and the earthquake i would get a 2s 30c 5000mah lipo packs(2 for the 8E)
on the earthquake, the 2 lipos are added together, totalling 14.4volts at 30c and 3200mah.(voltage doubles, not runtime)
so a pair of 2s 30c 500mah lipos will put out about the same power, but give greater runtimes.

now, on the caldera, a 2s 30c 5000mah lipo will be a big power increase. and runtimes will be 25 minutes or so.

lastly, lipos are not as heavy as nimh counterparts. just one more small advantage!

if the stock nimh pack didnt fully charge, it will indeed cause studdering.
when i 1st went brushless i found that my nimh packs didnt cut it. lipos are soo much better for the job.