The main differences between the two units is in the I/O (inputs and outputs) count, the preamps (the Digimax DP88 has digitally-controlled analog preamps, the D8 has regular analog preamps), and the sampling rate (the D8 samples at up to 48k, the DP88 samples at up to 96k).
Neither preamp is discontinued, and you can see them here:
http://www.presonus.com/products/DigiMax-Series