Don't post it up in the forum! Go to the BM Classifieds and post an advert or see what's on offer.
And if you can't see what you want then post in the Wanteds section.
Cannondale is fond of various wheezes to get people on shiny new bikes of its own making, and the latest one is potentially quite attractive. If you've got a Cannondale frame that's seen better days and are sorely tempted to replace it with a new, bang up-to-date, scratch-and-dent free one, the SI Frame Exchange Program (yes, they're American) could be for you.
It's straightforward enough, being a simple trade-in arrangement - your old frame plus a reduced sum of cash money gets you a lovely new one. Apparently they'll take anything, although we doubt that Mike's sixteen year old 3.0 Series (complete with approximately 50% paint coverage) would yield much of a discount...
Find out more from your nearest Cannondale dealer, whom you can locate with the aid of www.cannondale.com.