X-Caliber 4 - Trek Bicycle

X-Caliber 7 - Trek Bicycle

Significant upgrades over 4: 9-speed drivetrain, 100mm travel fork(vs 75) w/ lockout. Other than those two things, you're not really getting a whole lot more for your money.

I know it's not for everyone, but I would suggest at least checking out some of the used options in your area. Quality of components does make a huge difference and $600-800 will go far on the used market.