Not so sure you should do this. I sold my 2's and purchased the RAAL towers. With the new Rymik dual 8 sub, you could fill the upper mid bass.
I am thinking of selling my RAAL towers and buying the Sierra 2's again with a new sub.... I purchased the wrong color towers too is what is pushing me to do this.
Sold my bookshelves on the Audioholics sales forum.