just got hold of the new ZX5 recently and got the team C factory car for my son at the same time, the Team C is good but tbh you can see where the extra money goes on the Kyosho kit, The kyosho kit is blinged up out the box you wont find any plastic arm holders and the kits just go together better imho than anything else I have built, I know this refers to the ZX5 but I dont see the RB6 being any different in material spec and design tolerance, I also run the RB5 SP2 and the handling on this kit is superb, the Rango looks good also but the few at our track have had some issues blowing new bearings which if it happens mid final can be a problem , I carry a grand total of zero spares for the RB5 and touch wood had no problems breaking anything so far which is just as well
personally I would wait for the kits to arrive and see if the price is accurate or not as this might be a suggested price and im sure those shops taking pre-orders have only taken a deposit just incase this happens, if you get the Rango im fairly sure you will be happy with this car also, as stated you wont regret spending the extra on the RB6 and you probably wont be to unhappy spending less on something else at the end of the day its your choice and as the RB6 is not out yet its difficult to make an assumption on how well it will go, that being said the last 3 versions of the RB5 have been gooooooood out the box.
p.s. Tebo did alright with the proto version and seeing as the official release shots came out soon after im guessing his car was close to production spec.