DVC is not offering incentives for add-ons at the "sold-out" resorts so you are looking at $92 per point for those. You can add-on at SSR for $98 per point, and if you get 100 or more points they offer the $8 off per point. The benefit of adding on thru DVC is, of course, convenience. Also, you would get current year points (maybe even 04 points, but you'd have to check on that one).
For resale, the best time would be when the contract comes available that fits what you want. Now is a great time to buy thru TTS if you are looking specifically at smaller contracts (100 pts or less) because they have reduced the closing costs charged for those contracts.