The basic character of the Vandy 2 is very different from the deCapo (I don't know the GMA). Both speakers do feature a relatively "polite" high end so your concern re: long hour/fatigue shouldn't be an issue with either choice. But, the Vandy's have both much more bass extention and more overall energy below the mid-range which shifts the octave to octave balance toward a warmer character while the deCapo feels more analytical (if you're not a fan of this tonal character) or tansparent and detailed (if you are). Choosing between the 2 is really a matter of personal taste, but I suspect that almost everyone who auditions these speakers will have an easy choice:
Personal priorities will take you one way or the other, but you probably won't have a hard time deciding.
One other note: If you keep your sub, you may be able to "dial away" some of the difference. I'd personally suggest that you consider budgeting $500 to $600 for a Velodyne SMS-1 sub controller if you decide to keep your sub and add the deCapos. It's a great product that includes a flexible active low pass, a more basic high pass, room analysis and PEq. The SMS allows seamless integration of your sub and mains and also allows you to eq for smooth response in the deep bass.
Marty
