Just a few caveats to note about the 5560IPT - not sure if all are still relevant, but they may be worth checking into:
1. For bridged extensions - important in a trading environment - each 5560IPT Turret counts as two phones against the system maximum. With an MXe controller the system maximum is 32 bridged extensions, so a bridged extension could only appear on a maximum of 16 turrets. With the MXe Server, the system maximum is 250, so that a bridged extension could appear on 125 Turrets (assuming it doesn’t appear on any phones).
2. If Privacy “on” is the default, then a privacy release toggle button can be on the Turret. If privacy “off” is the default (common in a trading environment), then it cannot be turned off (i.e. no toggle button to turn it "on"). This is a Mitel oddity. NOTE: There is a Flash demo of the Turret floating around somewhere that shows a privacy enable button, but this is likely incorrect.
3. Not sure if this is different when recording the 5560IPT, but on the 3300ICP when using MiTai for CTI triggered recording, MiTai doesn't work reliably when there are more than 16 lines on a phone (important in a trading environment). Recording can be done without CTI, but then there is only limited information about a call.
4. Not 100% sure if this is really the case, but I believe that in the 3300ICP Prime line select can only choose the primary extension - no option to have no line selected so that a manual choice can be made without first hearing dial tone from the Prime Line. Not a deal breaker, just another curiosity.
5. Mitel YourAssistant can only be associated with one line.