My .02. Don't upgrade the old bike if you are talking about this kind of commute for a long time. You need a good bike you can count on. That Kona is nice, but the Bianchi is a better choice, I think. The reason is that the drop bars will give you a much better variety of body and hand positions. When you are bucking a strong headwind, you will really be glad for the drops. As for the money, think of it this way: it costs about 6 cents a mile to drive your car. You will save about $11 a week riding your bike. Therefore, you will have a "free" bike before the end of the year, and she will start making you money after that! So, get a girl that you will be proud of.
A second piece of advice, come join the XCC (extreme commute club). Lots of great advice and support for your commuting. Everyone will love to hear all about your adventures.