A CD 1.83Ghz will make the deadlines easily if it folds most of the time.
My CD 1.66Ghz does one frame of a 2651 in almost exactly 30 minutes, and a frame of a 2610 in 34 minutes. Folding constantly, it would complete the WUs with respectively 48% and 41% left before the deadline.
So you only really need to fold just over half the time. If you can leave it on for long periods and you don't do anything else performance-intensive, I would go for it.
I get about 800ppd on a 2651 so expect closer to 900 if you leave it on all the time. The noise might just drive you insane though, that's why I don't run SMP on it constantly!