I have tried poly seal with the 105...and Poly seal contains a wax in it so it made the 105 slump off a bit as far as lasting....
if doing the DG system..I would use either the 601 or 101 or 501 as a base..all are sealant based and no wax to interfere with any bonding issues....
The 601 does add duribilty as I have tested with and with out over the last winter..and with it lasted longer...with out it went from Nov to April...with it to late May before I redid the car and it was still doing good and could have went longer....
the way it was explained to me was the residue that is left on the paint with out buffing it off reacts to the 101...111...105....to harden the shell they leave on the paint...
I only use 601 for the winter use...during the summer I use 101 or 501 as a base since I can redo it it any time during the good weather if needed..but when its cold and snowing it just gets 601 and 105 put on in Oct or Nov to last the winter....
AL