Hi guys, I've been trying eyefinity recently and also got confused about this problem. But somehow, I think I figured out the reason and I want to hear you ideas.
-First I think we need to agree 1 thing that we need at least 1 monitor connect to miniDSP port on the card.
-Then, we need to consider Analog(A) signal VS Digital(D) signal.
-Now, this come to what people arguing on the net. MiniDSP/DVI-I send out both D and A signal.
-If you use DVI-I to VGA or MiniDSP to VGA, they take only the A signal and send thru VGA cable to the monitor. That's why people say they can use passive adapter, because it is analog (continuous signal). So, If you have old monitors with only VGA port, they should work w cheap converter miniDSP to VGA (around $10 on ebay, Which I'm using now).
-On the other hand, if you use MiniDSP to DVI or MiniDSP to HDMI, they will take the D signal, now, I heard that (not 100% sure) they use some kind of clock to control the signal between 2 ends. So, that's why you need active converter or some built-in chip converter.
To wrap up, it's not about active or passive, it's about what signal you want to use. And I haven't try D signal so don't ask what's the difference in quality on the monitors.
Well, hope that answer the question, if you think I'm wrong feel free to correct it.