Just make sure you have a great shim job and get solid metal bushings and not bearings Here is a list of all the things you should get
Motor:
http://airsoft-club.com/shop/internal-u ... -long-typePiston:
http://shop.ehobbyasia.com/upgrade-part ... -blue.htmlMosfet: for this one you have a WIDE range of choices depending on what features you want and how much you want to pay this
http://www.awsairsoft.com/sentry would be a good one because it monitors the cells in the lipo and if they go too low the gun will shut off.
Lipo:
http://www.hobbypartz.com/83p-2650mah-3s1p-111-30c.html that one will get you an incredible rate of fire
Lipo charger:
http://www.hobbypartz.com/thac6smbachw.htmlThis setup will give you a really good rate of fire also im not sure what you have in your gun but you might want to get a new piston head too if yours is metal
Piston head:
http://shop.ehobbyasia.com/upgrade-part ... -head.htmlSorbo pads:
http://forums.airsoftmechanics.com/inde ... pic=1446.0 these will make you gun alot quieter and put less stress on the shell
You do not even need to get the lipo in this case it would probably also put you over your budget but this would definately be lipo ready and even with a 9.6v you would have a very good rate of fire you should probably look up alot of guides on how to shim the gears if you have never done this before and if you are not very good at soldering you can send your gearbox into the company that sells the mosfets and they will put it on for you. You also might want to run a m110 if you are going to a lipo just to avoid premature engagement