Do you really have to let one go, or is it just your mind telling you to do so?
I went from having a 2000 SC superlight to a 2007 frame and then last year went with a s/hand Mojo SLR frameset from these classifieds whilst at the same time going to new 34mm 150mm travel forks.
The ride on the SLR is awesome. Much much stronger feeling than the Superlight, but I do miss the SL. So much so that I’m thinking of dismantling my HT to build the SL back up.
Morel of the story is that if you really don’t need to get rid of one – then don’t and simply ride which ever one takes your fancy at the time.
Especially combined with the fact that you won’t get much for either.