The word for speed is economy. If you want to play faster, your movements have to be as powerful, but with less motion.
When you see speed devils on http://www.chopsfromhell.com those guys barely move their right hand, and their fingers lift so little from the keyboard that you barely see them moving.
Of course, the compression given by your amp helps playing legato phrases with less effort.
Study Allan HOLDSWORTH for legato, the guy inspired Satriani.