Network Topology

I need the expert advice from all of you in this issue since my experience is insignificant compared to some of the members of this list. In your experience what is better in terms of connectivity to the Internet. My boss wants me to order 4 T1's (maybe 6) to different providers to be 'completely' sure that our NOC will 'always' be up & running. I've already got 2 T's right now, I really don't know how' 'wise' it is to add another 4 or 6 from 'different' providers. Would it be better for us to get them from the same 2 upstreams we've already got? Would it be better to get a Fractional T3? I need some convincing arguments for him to understand, can anyone help? -Victor