I have a client with a dk424 - 12 CO Lines, 8 analog ports, and about 96 Extensions.

They are asking if their is an upgrade path for them that would allow them to keep the phones. Which are primarily DKT-2020SD

From what I can tell a CTX 670 could be the best route to go. Am I on the right track? Are any of the expansion cards in the DK424 compatible (not expecting them to be).

any gotchas I want to be aware of?

thanks in advance,
Michael