I WOULD RECOMMEND THAT YOU GET THE 925 BECAUSE ITS NEWER CPU, IT WAS RELEASED IN JUNE 2006 AND THE 930 WAS RELEASED JAN 2006. SO THE 925 IS PROBABLY BETTER, AND MAYBE EVEN RUNS COOLER. EITHER THAT OR MAYBE ITS BETTER CORE OR SOMETHING THAT INTEL DECIDED TO USE.
The 925/945s are pentium Ds that intel are making due to conroe. Core 2 duo is faster/cooler/more efficent uarch and intel doesn't want to have several products in its product line. They are mearly a cpu to:
a: Replace the entire pentium d product line with only the 945+925, meaning it does not cost so much as they don't have as many chips in the portfolio. Intel saves money by using processors that couldn't reach speed X, changes the multiplier, disables a few features and rebrands them as a newer processor.
b: To fill the lower/ value segment of the market as they are cheaper than their core 2 duo cousins.
They probably have a few changes as the newer models are perhaps revisions of the old core, B1, however I would not bet on it that there is a noticable difference between the two (power conusmption etc...)