With one computer, a non-Pro
Mac, you will not be able to output 2 separate feeds. Unless you use the Matrox box. Even then, you'll need to use some sort of software (in this case Isadora) to parse the "
monitor" feed to the correct
screen percentages. Izzy is something like $350 and a DHTG is $200. That's the cheapest (except using a DVD...). Setup is exactly what metti said, easy and well documented.
A
Mac mini would run $700 for new a little less used. Run the licensed version of Izzy on the iMac and the no-save version on the mini. A patch could be written for the mini which "listens" for
OSC or TCP and any video /sound
cue could be fired in relative sync with both machines. The patch for a single machine with a DHTG is a little more involved, but doable.
The thing to keep in mind is
processor overhead. An iMac will strain with a DHTG with two separate feeds, one being "live video feed plus effects". By spreading the processing out over two, you'd definitely be able to run both feeds at closer to native res for the displays.
The other option would be to rent a Hippo from an AV provider and be done with the whole thing
in one shot. I guess it depends on your 1. budget and 2. longer-term needs.