Mike I have a RS4 rtr3 for sale right now
I bought it in the rtr form and have made a ton of up grades with the intention of racing it, which I did a couple times. Now the track I like has cancelled thier Sunday afternoon racing and now they only race on-road thursday nights(hard for me).

The nice thing about the RS4's are the availability of parts and the ease of repairs/mantainace. They are very easy to break down and put back together for cleaning and repairs.

I don't know about the Yokomo, but the thing with any RTR is you more than likely going to have to install upgrades to get the speed and handling you want. If you buy a "pro" kit you get all the top components, but you spend more money adding the engine and radio system.

anyway if your interested in a RS4 let me know and I'll make you a deal on mine
Good luck
Tom