I would think that a dedicated line is used to isolate your components from the rest of the items in your environment ie, dimmers, microwave, digitals, electrical motors etc. Given this, wouldn't it be advisable to further isolate the 'dedicated' lines by using a seperate ground system as well ? And then to keep one dedicated line for analog components and a second dedicated line for digital . Although none of this would 'clean' the incoming power it would, however, keep it from being contaminated further .
Just my thoughts, YMMV.
Just my thoughts, YMMV.