I was in similar shoes but on a smaller budget. I was more torn between 1.1 and a 1.2 but ended going with a Fisher Rail at a discounted price (since the Fisher line is going away and melding directly into Trek), which is about in between a 1.1 and 1.2 as far as specs go. I sat on and wanted a 1.5, then saw the 2.1 and felt the same. I left the store, came back the next day more level headed realizing this was my first real road bike and decided on the Fisher. In 3+ years I'll likely upgrade to something better but thats assuming I'm still very much into the hobby then as I am now.

Ultimately always spending more is going to seem better, but it comes down to needs. If getting the 105s is important (trust me I wish it was for me), then spend the extra few hundred and be completely satisfied with your bike, no buyers remorse. If you're thinking about already regretting a 1.5, my advice is just to get the 2.1 and grin walking out of the LBS. If being practical is more akin, get the 1.5 and perhaps part upgrade 105s over the coming years (even though it may cost more in the long run).