Custom workstation help

Hello all!

Just need a bit of help in deciding some parts for my custom workstation build. This machine will be used for my Computational Finance classes. A lot of C++ coding, computer simulation that makes trading decisions. But would like to add some fun to the mix as well because this computer will be used as an entertainment, HD movies, games, web browsing, itunes, etc.

My ideal budget would be $2000 but I am willing to be a little flexible. So far i have decided that I want an Intel Xeon E5520 Nehalem 2.26GHz LGA 1366 80W Quad-Core Server Processor that supports ECC Memory of at least 6gb. Question is, buffered vs unbuffered vs registered vs unregistered for my needs that I specified. I am extremely confused in the ECC area.

other parts that I have chosen,

EVGA GeForce GTX 460 (Fermi) 1GB 256-bit GDDR5 PCI Express 2.0 x16 HDCP Ready SLI Support Video Card

Intel SSDSA2MH080G2R5 2.5" 80GB SATA II MLC Internal Solid State Drive (SSD)

WDl Caviar Black 1TB 7200 RPM 64MB Cache SATA 6.0Gb/s 3.5" Internal Hard Drive

SAMSUNG P2450H Rose Black 24" 2ms(GTG) HDMI Widescreen LCD Monitor

CORSAIR Cooling Hydro Series CWCH50-1 120mm High Performance CPU Cooler

I also need a compatible Motherboard but undecided in this area as well.

Thanks you all in advanced.