My metal influences are Rhapsody (of Fire), Bal-Sagoth, Therion, Helloween, Symphony X, Angra, Necrophagist, Nile, Death, and Iced Earth. Those are at the top of my list, I do listen to classical but not jazz, however as a bass player I have studied a little bit into jazz and respect it as a musical style.
I also agree with you guys. Also, I always thought it was cool when there is clean or high pitch vocals that underlayed a harsh style of vocals for choruses or when there is a new verse.
I don't listen to Mushroomhead, so I don't know what there vocals are like but Adagio is the band I know of that does it really well. Especially on their Dominate CD.^ A band that I know that does this is Mushroomhead. They're not the greatest band or vocalists for that matter but that's where I'm trying to get at with the high vocals and low.