I went with IP office last Year, started with SOE, then 406v2. I used to have Magix 3.0 with 412TDL, 024TDL, 408MLX-ICLID.
You can use the 4406, 4412, and 4424 phones on IP office!
I cut My monthly phone bill in less than half with VOIP calling! Plus You can have up to 64 Way conference calling!
I have had up 7 way conference so far, very clear, I'm impressed! Magix/Legend You can only have 3 Way calling, plus 2 extra interal parties.
I am very happy with IP office. If You are going to stay with analog pots/did service, you might as well keep Magix. Magix is a very good system, I had it for 6+ years with NO problems, except a few froxen MLX phones which were left over from when I had Merlin Ledgend.