Its not really about top speed, anyone can gear their bike for top speed, its all about low down grunt. I'll take lifting the front wheel every gear with just a twist of the throttle and a low top speed over lack luster acceleration and a high top speed that takes forever to reach. And dont go by the specs on the manufacturer's websites, they arent even close to accurate. An atomic with a lifan125 is just as fast as a dhz or any other brand with a lifan 125. The difference in price usually indicates the difference in suspension and chassis which is what will make it faster on the track but if you only care about straight line speed buy the cheapest one with the biggest engine or just go buy a crutch rocket and forget about dirt bikes