What is a RCXRAY? If you are referring to the XRAY M18 and you are going to be running it outside with us on asphalt, you probably won't like it.

I wouldn't trade my 18R for a M18 and I own both. Parts availability is greater for the 18R and parts prices for the 18R pale in comparison to those of the M18. The M18 is good on carpet and smooth indoor asphalt surfaces but lacks damping to absorb asphalt inconsistencies. The M18 is also pretty much limited to foams for grip.

You don't need to purchase the Exotek right away for the 18R, you can be fast without the Exotek though I believe that the Exotek conversion has greater potential to be faster but also makes the car more difficult to drive (In modified).