Hi Ramesh,
For the isolation of the Silverstone card, look here :
Re: USB to PC chassis ground ? (noise) - Bracket.
Mind you, that post from my hand only shows how we did it but you will find more good pictures and good ideas in there from others. It is thus about the idea.
People always do it themselves, as we don't even sell / deliver the card.
Also notice that the "isolation" as such is only about the isolation from the PC chassis at that point. Via other ground paths in the card and in the PC, the (ground) connection is there again, but via another route.
For more understanding (of our (all) own understanding), you can of course read that whole topic, if you have a few spare hours.
Regards,
Peter