You can add either DEN-SFO-PHX or DEN-LAX-PHX into the route for a few extra miles with not too much extra cost...
or you can do something more adventurous like:
COS-ORD-MSN-DEN-PHX on 2/2 and
PHX-ORD-BWI-DEN-COS on 2/8
Found on .bomb for $559.30 all-in. Nets out to 6890 EQMs.