For applications with a large amount of monitoring thermocouples I have used the Watlow EZ Zone RM modules in the past, although I never have tested them for accuracy. As I recall it was quite a cost effective solution and I never heard any complaints from customers (like I have with Flex IO TC modules).
I used them with a CLogix PLC, but in theory they would also work the Ethernet IP ignition module described above.
Good Luck!
Lane