If you get a revo I would suggest either the OS .18 TM, the OS .18 TZ, or the Sirio .23 engine that is designed for the Tmaxx/Revo. The TM gets about 1.6 hp and you can put the EZ Start on it. The TZ gets about 2.28 hp but you can NOT use the EZ start and this will not work on a tmaxx, you would also need to get a starter box (about $50) to start the TZ motor. The .23 has alot of power and can use the EZ start. Most big block engines will not fit the Revo (unless they say otherwise) without the big block installation kit($50). The savage comes with a big block and has alot of power out of the box. Most big blocks will fit in the Savage with out problems.
Oh yeah, the stock TRX 2.5 has about 1.3 hp. I would also suggest the wide ratio 2 speed gear set for more speed out of the Revo($7).

http://www.teamtrinity.com/sirio/23/sirio_23.html
http://www.osengines.com/engines/car.html
http://www.traxxas.com/products/nitr...ccessories.htm