Matrox has a PCIe P650 (2 outputs), and it will work with the SLI board too, and would be able to work in tandem like the other options. But if you want the monitors, 1 cards, your options are limited.
2 X300SEs (or GF6200s) would work also, but it depends on if you want the best 2D and multi-monitor support, or whatever does the trick.
are there performance benefits or penalties for using a pair of PCI express cards in NON SLI mode vs using the PCI Matrox 4-monitor card.
Not really performance benifits so much as quality benifits. If you run ultra high resolutions then you'll want a more modern card from either Matrox or it's competitors, something with faster RAMDACs to support higher resolution with higher refresh. But even then you may not notice the difference because you'll not be limited by the cards' performance so much as your information source giving you information need to refresh your screen.
Even for running models, you're not going to see much difference.
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