Is there some way to test a system for too much jitter? Hmmm...I guess you could get your hands on a DIP and see if it made an improvement in your system. If not, then I guess your system doesn't have much jitter!
Sorry - I'm just not very savvy on these issues. However, if I were you, using the digital out from an SB3, I wouldn't bother with a DIP (or any other anti-jitter device). As there is no mechanical movement in the SB3, it seems like the single largest source of jitter from your transport is already eliminated. Furthermore, if you do a little googling, I bet you can find analysis of the SB2/3 and the amount of jitter it produces. I'm pretty sure I've read references to this, and the jitter level is pretty small.
[Just for completeness - antijitter devices don't necessarily lower jitter anyway. Due to their electronic nature, they can actually be a source of jitter. If I recall correctly, the DIP measured pretty well on the additional jitter dimension (relative to severeal other affordable anti-jitter devices). But if jitter is almost non-existant from your transport, something like a DIP still seems more likley to be detrimental than beneficial.]
I have a DIP 24/96 that needs to go back to Monarchy for repairs. Once it's fixed, I could always send it your way for a quick test. It's destined for audiogon once it's operational anyway. Let me know if you're interested.