I agree that a 30mm deep wheel with the right tire will beat out the shimano wheels. However, it gets tricky here, I know 0.00 30mm deep wheels that are wider than 19.5mm at the rim. The problem becomes finding a tire thats not poop slow. Continental, Bontrager and Hutchingson all make 20.0mm wide tires, but all of them have bad enough rolling resistance to not be worth their aerodynamic advantage.
To make things more complex, depending on your size and your type of racing, you may choose one over the other. A smaller racer in shorter events would be better off with the 30mm rim with maybe a Bontrager aero wing tire. A larger racer in a longer event would probably be better off with the shimano and a good tire like a Vittoria Corsa CX or Michelin Pro Race or Bontrager Race X lite pro.
Here is a test, you can see the shimano tubular 24mm rim kicks ass, and the Shimano R560 is not that far off the Xentis Mark 1, ahead of lightweight ventoux, and ahead of the Fulcrums the OP mentioned by a solid 2 watts.
I think the Tour test isn't the best wheel test ever(the Hed 3 result is atypical from the 3 or 4 oher data sets I've seen), but it definately offers some good baseline numbers.
Best budget option would be as follows I suppose. A Shimano R560 in the rear, with a wheel cover and Vittoria Corsa CX tire; paired with a 30mm deep rim with a Bontrager 20mm Aerowing TT tire on the front.