I find In Ear Monitors helpful but don't really enjoy them. They can be inconsistent and you need a good engineer to run them. For singing with loud bands, I understand why you would use them but I would say that it's much harder to mix in-ears if you don't know the band.

ChristopherSchlegel is right, I would also encourage you to check various audiophile and musician websites before buying. Some sites where you may see discussions of best brands are Head-Fi, StereoPhile, HeadphonesUnboxed