The work of the modders here, and hopefully future stuff from OBD, just got me wondering.
This should not be an issue for me for a long, long while but just so I am ready (or come across some money I just have to spend) I guess I am seeking opinions or facts if anyone has them.

Does WOFF (or the CFS3 graphic engine if that is more proper) efficiently use two graphics cards (SLI) or would someone be better off with one super-duper graphics card?

Based on what I know, which I will admit is not too much, I would think one very high-end card would be best?

If you have one card and can get another similar one pretty cheap (and you have the right motherboard) then SLI might be a good idea for the money. I have read that two HD7750 cards are not quite as good as one HD7850 card and the price is similar.

So, to answer your question, yes a good high-end card is normally better. (not that I have actually tried it!). I have three cards but they won't talk to each other anyway! And my mobo has integral graphics which won't talk to any of the cards either.

I tried using Crossfire several years ago with OFF3 and the FPS were worse with two cards than when I disabled one of the cards and played the game.

Drivers may have changed that situation since then as well as AnKor's mod making WOFF use DX9 (versus the original DX8), so you can always try and let us know if there is any improvement with dual cards.

Thank you gentlemen for your thoughts and opinions.
Looks like, for a change, my instincts were correct

I think JimAtrill gave the most pertinent info when he said "(and you have the right motherboard)". To that point:

A couple years or so ago I was able to build a dedicated flying computer. I read reports and reviews on video cards and they indicated that two mid-range to good cards linked (SLI or XFire) would outperform a single top-end card that cost the same or even slightly more. Armed with this I decided that was the way to go and focused on XFire (I was looking at ATI cards) motherboards. I bought my cards individually rather than both at once and when I was getting 40-50 fps with one I was really looking forward to that second card.

Once I finally got it, plugged it in and fired up WOFF I was rather shocked to find that I had gained nothing. I started looking more deeply into the tech behind how all this works and found that my motherboard has 16 lines dedicated to the first video slot but if a second card is used it automatically reassigns eight of those lines to the second card. I had no idea that made a difference before and therefore had no reason I knew of to look for that information. And believe me, it's not information the vendors or motherboard manufacturers put up front.

So if you're thinking about going XFire or SLI dig deep into your board's stats and make sure that it provides 16 lines per card.

I investigated my Motherboard which is a Gigabyte 880GA-UD3H and it has "1 x PCI Express x 16 slot running at x16 (PCIEX16)" and "1 x PCI Express x 16 slot running at x4 (PCIEX4)". So the second slot is a lot slower in this case. There is no mention of reassigning lines at all. But for this mobo one fast card will be better than two slower ones I reckon.

Actually I'm not about to try it as I am getting an HD7850 2Gb card to replace my HD7750 1Gb card. It seems the 7850 is three times as fast. I cannot try Crossfire as the cards are not compatible.

If I remember, Jim, the cards only have to be from the same series (HD6000, HD7000, etc.) but regardless which one is in which slot your performance will be limited to that of the lesser card. And that, I believe, is a function of XFire not the motherboard.

Always better to go with one card IMHO as some games don't support SLI or XFIRE.

One thing to note is that adding a second card will not double your video memory, it will just double your bus speed. Depending on the game, this may or may not make a difference in gameplay. Also, the latency when communicating between the two cards might actually worsen performance and show up as stuttering in some games.

I always refer to the 'Best Graphics Cards For The Money' article at http://www.tomshardware.com/reviews/gaming-graphics-card-review,3107.html and decide from there.

I would have thought that but the AMD web site shows that the HD7750 and the HD7850 are not 'Crossfireable'. See their chart here which shows that the HD7750 is only compatible with itself or the HD7770. [url=http://support.amd.com/en-us/kb-articles/Pages/Crossfire-Chart.aspx][/url] http://support.amd.com/en-us/kb-articles/Pages/Crossfire-Chart.aspx