forgot to mention I have a yellow bertazzoni stove!

Without seeing your pictures it is hard to say. But I think that white subway tile would be the better choice so that you avoid the marble backsplash "competing" with the quartzite counters. The white subway tile would, in my thinking, make a clearer separation with the counters and you wouldn't have to worry about the marble and quartzite not quite matching, but not quite not matching. A yellow Berta sounds very cute!

Take a look at Emser's Mosaic Pattern Blends (linear Stone) in Ambrato! I saw it today (sample) at a friend's house and it looks very nice. I think it's a combo of marble and white glass tiles.

I second Francoise, and I've had both and loved them both equally.