I know 'sorenes doesn't indicate progress etc etc' But sometimes it shows you you're on the right tack. I rarely get sore, usually soreness is mild and just after I've started a new exercise.
However its a little different this time:
I have been doing crunches on one of those benches where you can rest your calves on an adjustable pad (see pic) now I've used heavy weight (~70lb) but was worried about neck issues. I finally decieded to use a jumpstretch band attached to a DB under the bench and loop the band (started with a mini and worked up, over the weeks, to a green) around my chest. I found this hard and it felt 'right' It wasn't until I added a litle weight to this set up (5kg + 2.5kg plate held at the forehead) that I really felt it, so Friday I aimed at 4 sets of 15 with 60sec rest.
I managed 15,15,15,8.
Flet sore Saturday and today. Obvious things like coughing and laughing hurt a litle (it's not debilitating) but it was nice to feel the abs working while walking my dog this morning, each time I corrected her for pulling I could feel my abs contract to stabilise my torso. And no she's not a big dog (40lb lab springer cross)
So in summary I feel the traditional weighted crunch does little at the top of the move, the band adds extra tension at this point making the weighted band crunch a good exercise, try it and see what you think.