Let me try to help....
your description is quite confusing...but I'll try to help. A few important things to keep in mind:
You will need a mixer (a digital one, preferably) to record multiple tracks of audio to your hard disk recorders. Ideally, you should buy a digital mixer that can communicate with your hard disk recorders using the digital format called "ADAT". You also will need a mixer (again, a digital one, preferably) to "mix down" the tracks recorded and stored on your Fostex hard disk recorders to a 2 track stereo master. To create a 2 track stereo master, most people mix down from their mixer to either DAT, MiniDisc, CD-R or even a computer. Again, I would recommend a mixer that supports the ADAT format, since all the Fostex hard disk recorders you mention should have ADAT "in" and "out" built-in. If you want to mix down to 5.1 Surround Sound, then you would need a hi-definition digital recorder (Alesis and Mackie make mastering devices that support multi-channel digital masters) or DVD recorder.
To answer your question...yes, you would connect your CD Recorder or DAT recorder to the digital S/PDIF outputs on your digital mixer.
Keep in mind that a single ADAT "jack" (or "port" or "card") can only handle 8 tracks at a time. So, since it sounds like you would like to record up to 40 tracks, you will need to buy a digital mixer that supports multiple ADAT cards. I think the Behringer digital mixer can handle up to 32 tracks using ADAT, but you will probably need to purchase additional ADAT "cards" for this mixer in order to support 32 tracks of digital audio in/out. Same thing with the Yamaha digital mixers (you will need to buy additional ADAT cards in order to support all those tracks you plan to record).
You will also need to sync these multiple recorders, using Midi Time code or some other sync standard. I am not an expert in this area, but I'm sure someone else can help you out.
I don't know why you would want to buy a VF-160 or VF-16, since you already own several digital hard disk recorders. You simply need a digital mixer. The VF-160 and VF-16 are digital hard disk recorders AND mixers, and their mixing capabilities are quite limited when compared to dedicated digital mixers like the ones made by Behringer and Yamaha (2 manufacturers that support the ADAT format). In addition, there is only 1 ADAT "in" and 1 ADAT "out" on the VF-160 and VF-16, so you would be limited 8 tracks of digital audio at mixdown. Yes, you can record 16 tracks simultaneously on these units by using an external digital mixer (or the ADA8000) to send 8 channels of audio via ADAT to the VF-160 (in addition to the 8 analog inputs on the VF-160). But this feature would not be of use in your situation, since you want to record and mix 40 tracks of digital audio simultaneously.
The bottom line - you need a GOOD digital mixer that supports at least 32 channels of ADAT digital audio.
Hope this helps.
ray
