Question : dsl modem with built router question

Here's the situation, our company has 12pcs and our dsl provider sent us 2 of those 1 port dsl modems with built routers. The reason they sent us 2 was that one of the modems can only support up to 6 connections. So we need two modems. So here i am wondering if

a.) the unit only contain a max of 6 nat address that can be used at one time hence the 2nd modem. However this poses another issue. I assume the phsycial layout would be something like this. 1st modem would lead into a switch which would server the first 5 hosts. The second modem gets plug into the switch #2 and will server the last 7 hosts.

 DSL modem/router
           |
          switch
          |     |
      host    Dsl Modem/router
                                  |
                                 switch #2
                                   |
                                  Host

How the thing I don't get is how would you get the 2nd dsl modem/router to point toward the first modem router? And would nat work properly in such a situation?

b.) we have our own dhcp server and we intend to turn off dhcp on the dsl modem/router. Provided that the first + 2nd router are on the same subnet as our dhcp server would we have any issues in having the host grab an ip?

c.) would our dhcp address work with dsl router/modem?

d) would it make more sense to just purchase a DSL router instead? If we use the equipment provide by our provider we spend nothing.

Answer : dsl modem with built router question

Well - you could stack them using the ports on the LAN side which would lose you 2 LAN ports but leave you the rest spare. One of the DSL line inputs would be used and the other one disconnected - that would probably give you a 10Mb hub rather than a switch unless the LAN ports can do more than 10Mb.
However I gathered from your question that they only had 1 x LAN port each.