I dont have any experience with the G-major but have heard good things...

I have a boss GT-8 and its effects awsome and extremley tweakable.If you need loads of amp models then the line6 route is a good idea.

Stay away from the GNX line unless they seriously overhaul the sound in the GNX2000,but I doubt it.It seems just a bastardized revision of the GNX line.Boss kills digitech in sound quality(and reliability)hands down.

I suppose if you have a rack setup and a space is free or want to build a rack rig,then the G-major may be a good choice.

I f you need good effects on the floor,then the Boss GT-8 is the best bang for you buck.