ok, server chipsets aren't any "faster" particularly, they don't offer more throughput, ok the woodcrest has a 1333fsb but it will make minimal difference and if as per usual server speeds are one or two behind desktop speeds the the extra cpu juice is going to affect stuff more.
the main thing, if its 10gb files hard drive access is going to be the single biggest bottleneck most likely. it can entirely depend on extra how the data is being processed. for instance if you are fixing a 4 gb dvd with parity files you ideally want to have the entire file in memory as the cpu will need to constantly access multiple parts across the whole 4 gig file, with only 2gb's mem you constantly page to the hard disk and are waiting almost entirely on the hard drives. parity files have to access the whole file, your program might not need such constant access to the whole 10gigs but merely part at a time. run the app, tell us how much mem and virtual memory it uses(you can go to view>columns in task manager to show virtual mem per process) and also check how much your seeing in the performance tab of task manager, commited memory, page file usage. if these are basically maxing you out you want more and more memory and as fast hd's as you can get.
os drive won't make much of a diff here. go with the pata, get 2x 320gb seagate 7200.10's and raid 1 them and have a 3rd one to backup all the data, or run 4/5 drives in raid 5, with raid 0 you'd have to manually back up your data but is basically the fastest/easiest way to use raid for speed.
for cpu, how much cash can you spend on this computer, assuming your cpu is running at 100% all the time grab a x6800 conroe, or drop down to another speed grade based on your available budget. its got the strongest fpu and should outperform everything else quite easily. the latest motherboards( i assume am2 ones aswell but not been looking) can support 8gb's of mem. this will mean win xp 64 pro edition, or going with a server edition but you can deffo use all the mem. 2gb sticks are far far more expensive than 1gb sticks. so again check the performance info in task manager, we need to know if you are cpu limited, hdd limited, mem limited or all. if the program is mainly using cpu and accessing data slowly then more memory and akiller raid 0 setup might not help too much. you might need all three maxed out in which case, again if you can afford it/fits into budget, then 4x2gb sticks will be your very best option.
definately let us know your budget and what the cpu usage, page file and physical mem usage tabs are telling us. that will give us a clearly definintion of where you need to upgrade and where you really might not gain anything.
as for gfx, theres the matrox triple headed card which would give you 3 screens with one card, not sure how much they go for anymore(or tbh, if they are even available anymore). or a couple g550's matrox cards(think thats what they are called, me goes to check). can only find one pci-e matrox card right now, not triple headed, theres an external box you can connect up outside computer to i think any gfx card, or maybe just matrox's to give an extra display, i think if you have two nvidia cards and don't hit the "enable sli" function you can run 3 displays but in sli you can only run 1, though that might be only 2 displays then only 1 in sli haven't used sli in a long time.
ok a pci dual head card can be had for £60ish, a pci-e dual head for like £80, mix and match, two of either, shouldn't really matter either way i don't think.