The 4-2-1 sounds great. Is super loud. I run a Ballistic 8 cell on my 750. Hasn't failed me yet. I run a solenoid off of a CBR600F2 on mine. Had it laying around the shop, it worked.
Here http://www.ebay.com/itm/1994-honda-cbr600-f2-starter-relay-solenoid-/262879623407?hash=item3d34d8b8ef:g:XywAAOSw8w1X6bvA&vxp=mtr