Thanks for your reply, Richard. I emailed Keith Williams (seems like a nice guy) and he explained the differences between the 19 vs 30. It boiled down to the 30 being perhaps a better all arounder, which is what I am shopping for.
BTW, I am about 5'7" 170lb and like to take long walks on the .... umm, never mind.
My current wheelset is fine and rides nicely, but is pretty heavy. I don't have the exact weights, but I put the front wheel on a little food scale that I have and it was roughly 900+ grams. I would guess that the rear is proportionately heavy as well. So I guess I am hoping to lose some weight (aren't we all?

) without giving up too much ride quality/stability. That might be asking for too much given my price point, but I am interested in hearing from others about what has worked for them as well as ideas as to which direction I might take.
Man, I
am wordy, aren't I?

The 30's would be a fine choice - I'm confident that you'd notice the difference from your old wheelset. Check out Psimet though - he also builds with the same Alu rims as Williams. Don't think you'd be quite in the range for medium rim carbon, but you're not too far off Rob's prices.