for indoor rc shots you need 2 things
zoom lens +100 mm
& zoom lens that is very lightsensitive lower than f4 value and with a fixed f
cause you can't use the flashlight because it looks bad and the long zoomlens will cast shadow on the pictures in some cases
and the indoor tracks usually have a very low light in general
So you should get something like a 80-200mm lens that has a fixed f value lower than 4 ! These are usually top of the line and very expensive 1000-2000€
(for indoor rc shots lenses with higher than f4 value will simply not do the job, most of them will not have a fixed f value so when you zoom in the value becomes f8 or higher)
outdoor use you could get away with cheaper zoomlenses because there is more light outside, however the cheaper lenses will lack the sharpness from a top end zoomlens. So the light will look ok in the shot but you will never get a super sharp picture.
in short : taking "pro pictures" of RC is buying a top of the line and very expensive zoomlens
the camera itself ? any up to date and good working body will do the job (in combination with a top end lens.)
So spend your money on the lens ! not the body
http://www.dpreview.com/products/nik...0-200_2p8_vrii
http://www.dpreview.com/products/can...-200_2p8_is_ii