I use a Magellan Meridain Color. I like it cause its color(a must with topo maps) and it uses a standerd SD memory card so its memory upgradable to whatever you want.
Magellan vs Garmin is really a personal preference. My best advice on buying a GPS is go somehere where you can play with a few different models and spend a 1/2 hour playing with them. Maybe do so some reasearch first to see what options you want and then go into a store.
I've had good experiences with
www.gpscentral.com, they have a store in the SE. Good selection and quite helpfull.
Another option if you just plan to use it in the Jeep is get a laptop and GPS card for it. Chepaer if you already have a decent laptop and more powerful(can do more things). But less versatile as its can not be easily ported around for things like GeoCaching or hiking.