[Raion]

The DCD on VPro and the dual head adapter for the O2 are not always the right call, for a few reasons:

1. They segment your memory in half for graphics. On the O2, with its VERY limited memory, this can be disastrous.
2. They don't have good compatibility with certain applications, especially legacy ones.
3. They reduce video performance since both framebuffers are driven by the same GPU.

The RAD4C and other PCI cards I don't recommend. At best you'll get an 800x600 unaccelerated desktop that will potentially interfere with your main desktop

If you want dual head, the easiest to do that on is an Indigo2 IMPACT where you can physically put two Solid Impacts into it, or you can get an octane and run two MXE/SE with TRAM boards in it.

Conclusion: Get a different machine if you expect any kind of acceptable performance and/or don't want to track down rare and expensive peripherals.