Mountain Bike Riders, Question

Mongooes use to be a higher end bike maker but lately (quite a few years now) the Mongoose brand is associated with the box stores. Mongoose still makes a few higher quality bikes but in most instances they would be a "pass". The only place I've ever seen the Genesis brand is at Wal-Mart.

Some that may be candidates:
Trek
Giant
Cannondale
Specialized
GT
Raleigh
Fuji
KHS
Jamis
Sant Cruz
Scott
Yeti
Kona
Orange
Lightspeed
Moots
Seven
Erickson
And on and on but these come first to mind. Some of these would be very expensive bikes but you never know when someone is unloading one at a killer price......

You will need somewhere close to a 20 inch frame, give or take, depending on your torso to leg length ratio, and that size will probably not be available in a box store bike anyway.