Yealink is #3 already for a reason - the best value for the dollar.

#1 Cisco is losing share, overrated phones.
#2 Polycom is great, but overpriced
#3 Yealink - the most beautiful phone on Earth (T48), phone variety is great; provisions easily; they will pass up Cisco and Polycom, give it time.

(#1, #2, #3 market share)

Grandstream would be in the top six also.