Should i upgrade?

[suicideneil]

The erevo with a few choice tweaks will pown the old emaxx platform any day of the week, hands down. The old hvmaxx setup is okay, but you should upgrade to the 5mm sintered rotor (kit) if you plan on keeping it to power an erevo. Feed it a pair of good 2s lipos, or topend 7cell nimhs and it will be good for 35-40mph.

As for the emaxx roller price, it depends on the exact list of upgrades you have, but parted out it will sell for a better price generally, again depending on the exact upgrades- some parts are getting very hard to find these days..