Kifaru makes awesome synthetic products. There tough, and dry very very fast. And they leave you with a dry feeling while sleeping in them. Those are just a couple reasons I switched from down. I got sick of having to dry everything out.
On the bivy comment, a bivy May or may not help, depending on what kind you get it may actually make things worse due to condensation.
I also own a wiggys bag and can tell you I won't be taking it on any trips where I'm carrying it on my back for any distance. It's a decent bag, but lacks a good neck baffle and is cut a little generous for me. Only reason I bought it was I needed a bag fast and was low on cash. I'll keep it for a car camping bag and something to drag in the sled on winter trips.
On a side note, the slick bag... My buddy didn't die in his 20* slick when temps went down to 15 degrees this last year. I can tell you he wasn't having a lot of fun though. I don't own a slick but use a kifaru woobie and doobie to sleep in. I plan on getting a slick bag in the future when money allows.