Need advice for choice of crank gear and rear cog ratios

I have ordered a new 2008 Baachetta Corsa S/S a few days ago, being a closet weight weenie I would like to put the bent on a diet and take the advertised weight of 22.4 lb to under 19 lb.
This is my question, the standard crank comes with the bike is a carbon FSA SLK MegaXO 53-39-30 triple and the rear cog is a 11-32 SRAM M970. If I want to change it to a double crank may be putting in a titanium road cassette what gear ratio will be most suitable. I live in an area doesn't have a lot of hill and I am current using 50-36 compact crank and 11-21 rear cog in my DF roadie.

Thanks in advance