Better gaming mouse?

I'm currently playing Borderlands 2 and I'm noticing some less-than-smooth scrolling when looking left and right. I'm currently using an older Microsoft Wireless Intellimouse 2.0, and I'm wondering if what I'm seeing is due to high screen resolution and low DPI on my mouse. Should I look into getting a mouse with higher resolution?

And any suggestions for something around $30? I don't play enough to rationalize an $80 mouse. The only specs I really care for are two thumb buttons and the clicking wheel (which is pretty standard now, right?).