Cari, you need to go do some research on XC bikes vs all mountain. In general, an XC bike has a shorter wheelbase, steeper angles and handles faster. All mtn is a bit more all purpose and is more stable on steeper, more technical descents.

http://forums.teamestrogen.com/showthread.php?t=7536

I have a 2001 Marin Mt Vision which has been significantly upgraded. It is not heavy and yes, it is very plush. The longer wheelbase and angles means it is more stable on loose, technical and rocky descents than a Racer-X. However, the Racer X excels the Marin on really narrow singletrack. You need to determine what terrain you will be riding and then look for a bike that works for that terrain.

I've ridden road bikes anywhere from a 49 to a 52 cm. I have long legs, a short torso and long arms. I probably don't fit bikes the same way you do. I think you need to look for a mtn bike with a long top tube and in very small size. Fishers are known for their long top tubes.