Honestly if you plan to tour with racks and panniers for 4 months you are going in the wrong direction. They bike you have would work better than all those bikes you listed. You are not going to get something lighter and faster than the Jake that is also better for touring.
If you're serious about the tour get something like the Surly LHT. It will probably weigh about what your Jake weighs, but it will handle way better with a load. If you want something that is zippier than a touring bike but can still handle some weight look at the Surly Cross Check, Bianchi Volpe, Salsa Vaya, and other sport touring bikes.
That Masi would maybe work ok if it was geared differently. For touring most people prefer lower gears. A popular setup is a 46/36/26 road triple like the Sugino xd, with an 11-34 cassette in the rear.
Last edited by pasopia; 05-15-10 at 03:11 AM.