welcome to RCM! A MMM, (Castle creations ) esc or Tekin RX-8 is the way to go as far as esc goes.
In a p-lot, w/a slash you will need a very stiff suspension to reduce roll. Make sure to keep x-tra diff parts on hand as well...
Mike, owner of RC-Monster, sells v/nice batteries here and they are v/good quality. If you are on a budget..look here...
http://www.hobbycity.com/hobbycity/store/uh_index.asp# A 25-35C rated battery should do nicely.
1. MBX-6 T8 1900KV, RX8 ON 4S
2. MBX-5T 1520, MMM ON 5S
3. MBX-5 ONROAD CONVERSION 1515, MMM ON 5S
4. MRX-3 ON ROAD CONVERSION 1512, MMM ON 6S
5. TEN T 2650 T8, MMP ON 3S