Hi. My son is looking to buy a mountain dirt jumper bike. I have been doing some research and have found out a few things but would like some expert opinions on this. I want to get him a low to mid grade bike with similar accsesories. I have found a few good used bikes with a lot of upgrades. What would you suggest I do...buy a new bike or go for the good used and get a better bike for the same price? Also what brand would you suggest as far as a reliable and quality brand. Any help would be greatly appreciated!! Thanks in advance