winter bag options

I have a GoLite 3 season long quilt that I have been comfortable to
freezing and with a few more layers think I can go lower.
I want to be prepared to try winter camping so need a 4 season bag or
quilt.

Does anyone just double up bags instead of having a winter bag?

I could get another GoLite 3 season regular quilt to double up with my
current quilt - weight of the two is the same as their 4 season long quilt
but save $100.00 and then would have another bag to share when it was not
winter.  Would the doubled up quilts provide same warmth as just one winter
quilt? or would body heat not transfer well through the outer lining into
the 2nd bag? The quilt compresses well, so I don't think the doubled volume
would cause a pack problem.  Is this just crazy newbie thoughts?

Thank you for your wise thoughts,

-- 
Ronda