We use the Yealink CP9xx series without issue, available in wired, wireless DECT, or WiFi models... Simple SIP device with excellent sound quality, and a fraction of the cost of Polycom. There are usually only a few of these on any one premise, so we hard code the VLANs in most cases. You are going to have to web in and manually provision them anyway, might as well just set the VLAN fixed as well. They do support DHCP options for that too, but not the same DHCP options as Mitel.