I've been using my Losi XXX-S that I've had since 2001. Matched with a Novak Havoc ESC and 21.5 motor it's plenty competitive. You have to remember - you're not talking about ridiculous speeds here so it's all driver skill. And the XXX-S was a full blown racer back in the day, so it has all the hop ups and tuning options you could want.
Don't spend a ton of money whatever you go with!
Losi XXX-T CR * Traxxas Revo Tekno Brushless Conversion * Losi 8ight 2.0 * Losi 8ight-E 2.0 * Corally RDX * HPI Blitz * Tamiya F104 V2 Pro * Associated TC 6.2