I have a DOEPFER A-100BS/2 modular and I love it ... I mainly use it for creating unpredictable sounds and then sampling them, cause with all those patch points its easy to make glamourous mistakes .. Ahhh the beauty of Analog synthesis

BTW You don't really have to build one, you can just start off with a full system like the A-100 then buy additional modules to add-on.

Get one :)