Linux – How to get different terminals for dual monitor scheme without X

Your computer power supply has nothing to do with running two monitors... they get power from their own power connections, and only data from the pc.

Most Radeon 4550 based cards are cheap little things, I don't see any that require a separate power connection other than what they get from the pcie bus, so there's no way loading them up with a bunch of work is going to draw enough power to really matter. And even then, mirroring the same screen on both is going to reduce the GPU workload, not increase it.

Short answer: yes, two DVI outputs is better.

VGA is analog. Since CRTs are all but extinct, VGA serves no real purpose these days. There are some very good reasons to choose VGA over DVI, but none of them are really pertinent for a home desktop computer. Using VGA means that you first have to convert the video signal to analog for transmission over the cable. Then, your LCD (presumably) monitor has to convert it back to digital. Usually this is done perfectly, but there is a chance that interference will cause degradation. With digital, it's basically an all or nothing affair. If you see something, the chance that it doesn't perfectly match what was intended is extremely low. DVI is a purely digital signal.

If you must use an analog signal, most graphics cards will allow you to use a DVI to VGA adapter. This is no worse than an output port that is VGA only.

Having said all that, will you actually be able to notice a difference? Probably not. But why chance it? If there are two cards using the same chip, and one has dual DVI and the other DVI and VGA, the latter is probably a lower quality card anyway. You're better off paying the extra money (if it even costs more) for the card with dual DVI.