Building an $800 PC for CAD and computations softwares

APPROXIMATE PURCHASE DATE: Either this month or Next Month

BUDGET RANGE: 600-800 After Rebates

SYSTEM USAGE FROM MOST TO LEAST IMPORTANT: Running Matlab, AutoCAD, MathCAD and some simulation software for Finite Element Analysis (Abaqus); Browsing; Office Products like Word, Excel, Access; Watching Movies; Games

PARTS NOT REQUIRED: Keyboard, Mouse, Monitor, OS

PREFERRED WEBSITE(S) FOR PARTS: newegg.com
COUNTRY OF ORIGIN: USA

PARTS PREFERENCES: I'd like to try the i7 but with my budget, it doesn't seem likely... I'd prefer either the LGA 1156 or 1366 sockets since it's more future-proof. Also, graphics card in the 200 series nVidia or 4000 series ATI line would be nice but not necessary.

OVERCLOCKING: Maybe
SLI OR CROSSFIRE: No

MONITOR RESOLUTION: 1920x1200

ADDITIONAL COMMENTS: My main reason for buying a new PC is because I will need a lot of computation power in the near future. I would like to be able to run Abaqus, Autocad, Matlab, Mathcad, Word, Excel and Firefox simultaneously. At this point, my laptop doesn't have the computing power to do this. Iteration in Abaqus takes painfully long.

I have a laptop that I can bring around so the PC is mainly for computing power.

The LGA1156 socket is essentially dead. There will be no more powerful CPUs than what's already out.

If I'm reading this right, you need an OS right? If so, you're looking at a $700 budget...

Here's what I'd build (tweaks may come):

CPU/Mobo: i5-750 and Gigabyte GA-P55A-UD3 $317
RAM: G.Skill Ripjaws 2x2 GB 1600 mhz CAS Latency 7 $115
GPU: GTS 250 $95 after rebate
HDD: Seagate 7200.12 500 GB $55
Case/PSU: Antec 300 Illusion and Earthwatts 430W $115
Optical: Cheap SATA DVD burner $22

Total: $719

I kind of forgot about coming back with an AM3 build...

It's fairly common knowledge that the LGA1156 socket will not be seeing 6 core CPUs. Intel's stated that they're making it their "mainstream" socket, hence the i3/i5 dual cores. That's basically the death mark for people who need a lot of CPU power.

So here's the AMD build:

CPU/HSF: X4 955 and Coolermaster Hyper 212 Plus $189
Mobo: Gigabyte GA-770TA-UD3 $80 after rebate
RAM: G.Skill Ripjaws 2x2 GB 1600 mhz CAS Latency 7 $115
GPU: GTS 250 $95 after rebate
HDD: Seagate 7200.12 500 GB $55
Case/PSU: Antec 300 Illusion and Earthwatts 430W $115
Optical: Cheap SATA DVD burner $22

Total: $671 w/ an excellent HSF

I would have liked to squeeze 8 GB of RAM in there, but it just wasn't happening without cutting something.

I should've mentioned. I don't need OS either, I can get it for cheap (student)