RBK753 and compatibility

I am thinking of purchasing a RBK 753 but first I want to know if it is compatable with my ancient modem I have.

My current modem is a Cisco DPQ3212 from COX cable.  (I use to have land line phone with it).  Will the new mesh system overload the modem?  Will the modem keep up with the speeds, or will it slow down my Orbi?  Will the Cisco not understand the "tri-band" signals or be able to feed the Orbi since it is older technology and may not understand how to communicate with a tri-band signal?

I hope that I can just purchase the mesh alone, and that my cisco will work - It seems to work fine for streaming internet and TV.  I just need a signal that will reach the basement and the far corner of the house.

Thanks.