Voger Design has created an "ultimate UI kit" including layout templates for a Kontakt instrument, Equalizer, Compressor and a Classic Synth.
The set of graphics of the Modern Audio PSD Kit is used in all 4 PSD files: EQ, Compressor, Synth and Mega Pack PSD. But every layout has its peculiarities and special features that make the UI creation very simple and meaningful. So, in case you decide to create a compressor, you don't need to buy a kit that has unnecessary controls.
Each PSD is well balanced for a specific purpose, and controls have right proportions and contain the layout idea.
Price: $199.