I still haven't gotten around to forking over $400 to Cycling74 - I don't doubt the value of the software, but I'm not sure it has value for me.
I've been using PureData most recently, before that it was Infinity from Sound Quest and QuantumFX from dbAudioware. Both are (were?) brilliant packages, neither has been active for years now. Pity!
I will have to see if there is an SFZ extension for PD - it seems to follow Max, so there might be.