very nice bike!
after riding an isaac sonic 2007-modell for several years (very expensive and light frameset), i got, for ästhetical reasons, one of those ebay-insolvency-isaacs for 600.- euros as well. it has a slightly different appaerance to your isaac. i graded it up with a 300 gramm-3t-rigida-team-fork.
love the ride, the geometry fits perfect for me.
beyond that, its a very stable and reliable frameset, i used it in many races without any problems. the price/performance-relationship of those ebay-isaacs is (or, better, was) unbeatable. (only the lacquering, it is durable, but a bit messy in some areas. i think, the ebay-seller (rockenstein-paintworks) painted those framesets without a pause!)
sorry vor mai bed englisch!