Another thing to consider it that Knopfler was known for not using his pick, but instead using his thumb finger-nail. His sound wasn't very heavy or over-driven for most of his music, though "Money For Nothing" and "Brothers in Arms" are notable exceptions. For his more classic style, like "Sultans of Swing" or "Telegraph Road", the picking style is going to be a quintessential part of his sound. To emulate that heavily picked sound, you may want to change the way you hold your pick, so that the angle as it strikes the string is more aggressive. The other thing is to try and get your thumb in there too, very much like a pinch harmonic. That should help emulate his style a bit more.