Let me correct the record.

The DS and DSX were designed by the "Nitsuko" team in Shelton. The merge with NEC had nothing to do with the quality of these products. (The DS-Series has the lowest return rate of ALL NEC key systems.)

FYI, the IPK-II software is the same as Aspire, which is based on the i-Series. The Aspire hardware is based on DS-Series. You do the math.