Synth.nl has published a nice series on building a PAIA 9700s modular synthesizer:
It was a lot of fun building and it was actually my first experience with a modular at all. And after building this I just wanted to build more. The kit supplied by PAIA is very complete and the instructions in the manual are very clear. I do think though that you need a bit of electronics experience to build this one.
Here’s a link to the pages in the series: