i have seen the Nova S5, a friend of mine who use to run RB's has 1 and is very convinced and he is very happy with it. He was still breaking it in when i first saw it, it ran good and very fast!!!
You should also check out M-Speed's RS12 (www.mspeed-jp.com
), price is around US$400+, ordered the motor direct from them. this is by far the fastest .12 motor i've seen around here.
How i wish i could get hold of 1 of Motormans motors, e-mailed him but he said that he is not shipping to this part of the world just yet
I would recommend the S5 though if regulations at your local track allow you to run these..