Is it a Proteus 2000 module? If so, I would jump at that chance in a heartbeat. I spent $450 bucks on one, and its a great module with lots of features if your work is MIDI based. At that price, I would wonder if something is wrong with it. Of course, it is also possible to find a diamond in the rough on occasion.
I got a Proteus 1 and 2 for $70.00 each and I have to tell you that they are both worthwhile units. If you have limited space they will accept inputs on the sub inputs and act as a simple mixer if you need.
Some sounds are a bit dated,but heck the thing is old after all. You can use it as a layer on top of another module and that is where you really benefit with these older modules. If you have an outboard filter that really gives you a total solution. After all filters are what make analog synths really awesome.