You may have trouble finding any bike that will be great for both downhill and x-country due to the varying geometries necessary for bikes to excel at the different types of riding. I ride a Pivot and highly recommend them. Lots of people love the Mach 5.7 as an all around bike. The Firebird is designed more for all mountain riding. I would guess that the 5.7 would be better at x-country while the Firebird would excel on the downhill. Here's a link to their website http://www.pivotcycles.com/ You can give the Pivot folks a call, too. They are very helpful.