I own the SF line 2 and the SFCD-1, I had my Line 2 upgraded a few months ago, with the SE+ and volume chips upgrade, the background now is much quiet, and the sound stage is wider with more details and resolution, however, you can still recognised the SF signature.
I had the pre amp couriered to Chris at PCX and after the mod couriered back to me, PCX used UPS services, buyer pays rtn shipping, and I live on the other side of the globe where PCX is located.
You can contact PCX for the mod details and option you can choose.