Upgraded to Arris/Motorola SB6121 today- still getting only 11+mbps on wireless network

Upgraded to Arris/Motorola SB6121 today.  I have Preferred Service in OKC (now 50mbps)  I am still getting only 11+mbps on wireless network using new modem and WRT54G2 router.  Tried to have tech on phone check my service code just to be sure, but he did not seem sure about  what I was talking about.  We finally  did get it installed and registered, but not sure about the service code for Preferred Service or about firmware on my modem.    Is there somewhere on the Cox site I can verify it?

Could the problem with speed be my router being an older model?  Attached are my modem signal levels.  

Upstream power level seems a little high.  What do I need to do at this point?  Appreciate any info or suggestions.  Thanks.