Intriguing project.
The three screens in the front can be manned by a single Matrox Triple Head 2 Go adapter, the two lateral ones on a second PC and the panel a third PC. All of this interlinked by Project Magenta or similar Sim sharing software I know little about at the moment, but that can be surely found on the net with little problems...
A bare minimum of three PC, two of which must be able to give good 3D graphics (
the one for the front view and the one for the lateral view) on which you better prepare to fork quite a lot of money, especially if you want to use FSX as a base sim. If you plan to use FS9 instead, it would require a more modest need for processing power and memory giving you more latitude with your funds. Or you could use X-plane, which would be a midway between the two above for graphical aspect and power needed, but I'm not going there because I know X-plane is appreciated by few (
simply presenting you the option should not be offense enough to make lynch mobs form, I hope). :-/
For the two most graphic intensive PCs, beside for the Triple Heads 2 Go video adapter to be used on the front one (
which is a simple to configure outside dongle with a single input and three different outputs for as many monitors), you would be good with the best combination you can afford of Nvidia Geforce card, CPU, memory and fast HD possible.
The second PC would need a quite good card too (
and I suggest Nvidia because ATi always were problematic to me) but not need adapters, as any good video-card nowadays has two video exits.
Seen you're stuck on Dell... beside giving you some general advice cannot be of a lot of help there, seen I know a little less than nothing about this brand of PCs. [smiley=embarassed.gif]
The PC responsible for the gauges can be less powerful under the point of view of the video department, saving you some money. And for last, a fast Ethernet linkage between the three PC is not an optional.
The hardware part is quite straightforward, if costly I expect, but the software part I fear will be
a waking nightmare more problematic, seen the only experience I have in the matter (
on the much simpler FSUIPC - WideFS combo no less) was quite hair rising. I can only wish you good luck and Godspeed. [smiley=thumbsup.gif]
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PS
You should ask in the HomeBuild Cockpits section as well. There you'll surely find more detailed suggestions.
There is no such a thing as overkill. Only unworthy targets.