RE: Paceweights link...
A set of 18 pace weights will bring a pair of dumbells up 4.5#, just .5 pound away from the next dumbell increment. That is what I would recommend.
(I have Platemates, but I bought the set of 18 Paceweights in the case--the magnets are very strong, and the case protects other objects from them, as well as protecting the Paceweights from impact that would weaken the magnetic force).