The JLR Red Dot .12 is the best value hands down. The motor is under $200 off the shelf and can hang with the Novarossi and Os .12 TZ Speed Tuned motors. You can even get it modded by http://murnanmodified.com
and really blow away anything out there. The only possible engines that would be faster IMO in a .12 are the modded Sirio STI EvoIII and the modded Novarossi 12-3SCT (I'm comparing a modded JLR Red Dot to these). However, the price you would pay for those 2 motors is much higher than you would pay for the Red Dot. Nothing out right now can really touch the value you get from this motor. Stock or modded.
Still waiting on the Ninja .12 which looks promising (dunno pricing).