You need to post more info on the frame you have and the new one under consideration. I just guessed and looked up CAAD 10 geometry.http://www.cannondale.com/2013/bikes/ro ... e-crankset
The suggestion to flip the stem up won't work, since you've already posted a flippped-up +6 degrees. I suppose you could use a +10 degree stem, but that won't get you much more bar height.
You need to think about reach, not just TT length. In the case of the CAAD10, the TT is 1cm shorter, but the STA is 1 degree steeper, so the reach is only about 6mm shorter on the smaller frame. You would need about 10mm more seatpost setback.
C'adale publishes the stack and reach, but when comparing the reach, there's a correction needed for the differing stack heights. Once that's done, the 52cm frame would have a reach that's about 6mm shorter. You get the samer answer, using either method of figuring the reach.
I would suggest trying lower bars by flipping the stem down on your current bike. I've done that, going from a 9cm saddle to bar drop to 11cm and it didn't bother me. You never know unless you try it.