Help with Advanced Networking

[DrBeau]

Note: I didn't know if this would be appropriate in the "Computer Help" section, as it's somewhat advanced.

Hi all. I know there are quite a few IT guys on here and I need some help. If you don't know anything about internetwork routing or routers, you may want to just stop now. Here is my quandary:

Here's the network setup:
http://support.siatech.org/temp/net-diagram.jpg

Here's the optimum way for things to run (this is as it runs now):

http://support.siatech.org/temp/optimum.jpg

finally, here are the two scenarios we'd like to work with:

http://support.siatech.org/temp/mpls-down.jpg

and

http://support.siatech.org/temp/t1-down.jpg

Thoughts? We'd like all this changing to be in the fly. I'm looking for a little direction as for what routing protocol to use, etc. Finally, here are some notes:

- I have no way of changing anything withing the MPLS, including the configurations of the routers directly on the MPLS.

- I can change the connecting between Router A and Router B to be a direct connection with a 2 address private network if need be.

- the IPsec VPN is the last route we want to be used for internal traffic for either Router A or Router B's network.

If anyone has ANY direction, please let me know. Even a link to a forum that could help would be great. Again, thanks.