Something I forgot to mention earlier in suggesting a Pentium with sound card might be usable as a dedicated DSP engine - the K6STI software absolutely required an ISA SoundBlaster. If we want to define a new DSP engine we need some higher level of abstraction to be able to cope with hardware that becomes unobtainable.
This is also a problem with other kinds of DSP engines out there - sooner or later you can't get the DSP chip and the A/D and D/A chips that you can today.