MrZammler,
I've been using a Delfina Flipper connected to the clockport of an X-Surf for several years in an A2500 with Blizzard 2060, PIV, X-Surf, Subway (on the other X-surf clockport) and a GVP I/O and have never experienced any hardware issues. I was experiencing the crashes/lockups caused by the delfina library but since I installed the updated version a few months ago, I have not observed a single lock-up/crash. I use it almost exclusively to play mp3s with AmigaAmp (mhi driver). I am quite happy with it.
Unfortunately there don't appear to be many programs that take advantage of the DSP besides decoders. I don't know of any.
I don't know why you would need to pipe sound through the PIV. The Delfina has AHI drivers and many outputs.