Im sorry Luke but the type of question you asked will always lead to many different opinions.
The fact is, all the cars are built for a purpose and all are capable of serving that purpose for what you want. Ofcause you will find the limits of the cheaper cars sooner, but again, each of them is upgradable.
What I recommend is to buy a "Racer" magazine, and then attend your local club. Don't be afraid of asking the people there, and watch which cars are doing okay etc..
My recommendation for your purpose is a RC10B4- RTR. RTR stands for ready to Run, and it is just that. You may need to change the tyres to suit where you race it but you will always need to do that with any kit anyway. In time the RC10B4-RTR can be upgraded as you improve and it can then either be upgraded and left as an RC10B4, converted into the S2 or you can choose the best car which ofcause is the X-6
