Hi Yelsel,
My first suggestion would be to not waste money modifying your current bike. Ride it for the time being, and save some $$ for a new one. In the meantime, go visit a few bike shops and test-ride a Bianchi Axis or a Cross Concept (instead of the Volpe). If you like one of them (or both) you can hunt on ebay and craigslist for one that's your size. Axis and CrossC are a better build than the Castro Valley and the Volpe. And on those you can change all the components you want.
If you still prefer either your bike or the Volpe, and if your choice is between modifying your frame with the clamp VS buying the Volpe - then I would suggest buying the Volpe, again because it will be easier to make changes/upgrades on that one.
On the other hand, if you plan to ride on the road only and you still want a Bianchi, I would suggest that you try both the Eros (steel). The carbon and Ti models would probably be out of budget even used, but the steel one shows up on ebay here and there at pretty decent prices. Bikes lose a lot of value once they are used, so buying on ebay is often a very good deal - as long as you have ridden the bike before and know that it is the right frame and size for you.
If you are not tied to a particular manufacturer - I'm a long-time Bianchista but there's a lot of other nice bikes out there - I'd say visit bike shops and try several bikes. Test ride around, identify a few models you like, make sure you know which size is right for you on those, and then go hunting on ebay and craigslist until you find your bike at a good price. We all can try to give you the best suggestions - but there is no substitute for test-riding a bicycle yourself.
Hope this helps!