^ +1 Any decent cyclocross bike should be more than adequate. Steel will absorb more shock than aluminum. I currently only have one bike: an old rigid frame mtn bike setup with moustache bars so I can stretch out a little. With 2in wide slicks, it will eat pot holes and is surprisingly zippy (especially for city traffic). 2in tires are overkill, but zippy is mostly determined by how you setup your bike.

If I was buying new I would look into a Crosscheck by Surly.