Yeah, Ultrasone's headbands and general clamping nature take time to get used to and they are definitely not everyone's cup of tea. When I first got them, I thought they would be horrible, but they definitely aren't bad. Before I knew it, I was watching full episodes of shows without even having to adjust them and take a break. But for all day stuff, I definitely couldn't wear it for hours on end (very few headphones I can). But, you can always try the additional headband mod found in the Pro 900 Appreciation Thread. Many say it improves the comfort greatly, but I haven't tried it so I cannot say. It pretty much looks like the K701 headband between the cups and normal headband, but it doesn't have bumps. If you want to see what it looks like, it's somewhere buried in that thread. You may not be interested, but you can always try it on your Pro 750 first.
The bass between the D7000 and the Pro 900 should be pretty close though. A member did an excellent review between the two if you want to read up on that.