Just got my new Catweasel MK4 in the comp with dual SIDs connected. What a result! It sounds wonderful, absolutely perfect in every respect. Very pleased here. I can't believe the difference in sound quality from the emulated version of SID. Just waiting for stereo SID support from Acid64 now. MK3/4 support will be included in the next release of SIDplay2/w. As I have asked Simon White politely to release an unofficial HardSID.dll for testing.
If anyone needs to get a spare 6581/8580 SID chip, then I would recommend you visit this site.
This guy builds his own SID interfaces for use in the SAM, but he also sells the SIDs separately at £9 each. Fully tested including postage, extremely nice guy.