Bike Selection Questions

[rtbo]

I am looking for a bike that I can use for commuting, group rides, touring, & possibly some cyclocross events (never done one but they definitely peak my interest). Currently I ride a Masi Vincere. I have become more ambitious with triathlons & will be ditching it in favor of a tri bike. With storage space being an issue, I'd like to get a bike I can do everything else on. I feel like a cyclocross bike will be the way to go but I have some questions. Any & all suggestions, criticism of the plan, suggestions of a different set up, etc. are welcome. Here are my questions:

1. What are the major differences in a road bike, a cyclocross bike (brakes & tire clearance?), & a touring bike?

2. Are panniers able to be easily attached to a cyclocross bike for both commuting/daily use & week trips?

3. What issues should I expect in attempting to use 1 bike for all these uses?

4. What bikes would you reccomend?

5. I will be building the bike from scratch, what avenues should I explore for finding good deals on parts (ebay, craigs list, bikes direct, local stores, etc.)?

I would like to keep the quality/reliability/durability high but am not scared of carrying around a few extra lbs on the bike to save a few hundred bucks building it.

Thanks for your help. I can't wait to get started on this. :D :D :D