You want bang for buck get a VBC dynamics D06. It comes with almost every tuning part you need. All the sway bars, all the springs, ti-nitride pins, multiple toe blocks, DCJ's, graphite AND aluminum chassis. All in one box. Best part is its only $475. Thats over $50 cheaper than the Xray is with none of those options. But hey you get ball bearing swaybars with an xray...
The VBC is pretty durable too after they upgraded their plastics when the D06 was origanally released.
So if you want a good quality car that you can probably get good help with because everyone has them but youll spend an additional $50-100 bucks on, on top of the $550 price tag already, go Xray.
You want a good handling, quality car at a great price that has everything you need, but will be harder to get help with as few have them (numbers are growing) get a VBC.
Or another good quality decent priced kit it the associated 6.2. Handles good, great parts support, and a ton of people have them.