I know that sounds boring but I need the forums help

I work as an exempt employee in a large corporate environment where the efficiency at which I do my job determines whether I work 45 hours a week, or 55. We're on windows machines built in '06 with Core 2 processors, a 1280x1024 display and all the slowness that goes with that. We upgraded from XP to 7 a few months back, we use Office 2010 and I use Excel and Access extremely heavily.

I may have the opportunity to assemble my own hardware and let my employer manage the software as a test for those who's work will benefit from upgraded technology. I'd like to build a PC from the ground up, as affordably as possible, that meets my specific needs. I've never done this before and would love feedback from the forum.

Processor: i7 if Excel '10 supports hyperthreading of if there is substantial gain over an i5
GPU: Digital support for 3 1920x1080 displays (3x hdmi or 3x DVI)
Storage: PCIe SSD 256ish or maybe 512ish
Memory: up to 16, not sure whats necessary but it's cheap
Components Not Listed: affordability is priority

Other Notes: Cheap sound is fine, I just plug in stereo speakers or a usb headset. I don't connect external drives etc but wouldn't mind a couple USB 3 ports just in case. I use Lync to video conference internationally but do nothing I would consider as GPU intensive like gaming. If I left anything critical out please let me know!

Thanks for the help!