I need computer for office-PLZ HELP

Have a look at the asus Z8NA-D6C dual 1366 server board; it's $259 at newegg. You can use one or two xeon 5502 socket 1366 cpus to go with it. They're about $200. For memory, crucial or corsair ddr3 will work fine; memory prices are rising, so I don't how much you can afford with your system budget. For the hardrives, 2 western digital cavier black edition at 750 gb each should be enough for data storage. I don't know how to set up a raid array, but you should be able to figure out which type will work best for you. I would avoid the so called "green" drives as they run slower and only use 1-2 watts less energy. The nice features of this particular server board is that it fits in a standard atx case, and can use regular non-ecc memory, which is cheaper.