hard to say on the weight difference if it is truly worth it, but at the same time every ounce counts because they all add up. there are only so many places in your gear to drop that much weight with one piece of equipment.
i had the DT1 late last year, and it was awesome....I didn't complain about it's weight even once i had all my attachments on it, because it fit so great it doesnt seem heavy. I do remember though when I had my Kuiu Icon 5000, when I picked it up I was always like wow this pack is so light!! Now, to have my already incredible kifaru pack at that weight?? it just makes an already great pack even better IMO.
you should be able to sell your frame for around $300 to $325 used if in good shape, so it's not that much of a loss.....but even if you keep what you have, that isn't really a loss either!