I am looking to get a sweet, smooth and singing sustain quality to the overdrive.  I really don't like the too rough edged Marshall like tones I have heard with some of the sound samples.
Does anyone understand what I am looking for tonally?  Also, can the Overtone achieve the tonal quality I am seeking or would it needed to be tweaked or modded?
If it does need some mods does anyone have suggestions for those mods?

The Overtone seems to be liked by alot of people.  There are some who think it can be made even better with some mods or tweaks.  From your experience with the Overtone what changes do you think would make the amp even better? 
What are the thoughts on the Overtone with the "HRM" circuit?  Basically what would this do to the tone?