I agree with the post above.
The rule of thumb, wich in most cases proves to be very accurate, is that the cheapest of brushless motor is still way better than tne most expensive brushed.
So ditch the motor + ESC, thats a minimum.
I also recommend swapping in the battery pack. 6s nimh is just not enough voltage.
You see, power is voltage times amperes.
but ampere causes lots of loss in the wires and ESC, but voltage doesnt.
So you want to get the most of your power through volts. Not amps.
Hence, a higher voltage battery is benefical.
3s lipo (11,1 volts) is the absolute minimum today. I cant think of anything that runs on less than 3 cells lipo.
You also get okay 4 channel 2,4 ghz radio for around 20$ if i remember correctly.
That will save you a lot of heartache with radio interference, old dodgy radio equippment etc.

So thats my recommendation: Swap it all in for some cheap chinese brushless setup.
It doesnt cost a fortune, and the cheapest of brushless, is, as said, way better than the most expensive brushed.