I would start with a careful inventory of all production software
you intend to run on a regular basis.
Let me give you a good example from our daily workload:
after we installed COPERNIC desktop search software
on a quad-core Q6600 workstation, we compared it
head-to-head with a dual-core D 945 in a similar workstation.
The Q6600 finishes just about twice as fast as the D 945
updating the very same 5GB database.
That can only be the result of parallel programming in COPERNIC.
If your software is not coded to exploit multiple cores,
you're wasting your time bulking up on multi-socket systems.
Those are intended chiefly for busy servers with lots of
multi-tasking to process.
After you've completed your analysis of your production software,
the real choice for you is between a single-socket Core i7 machine,
or a twin-socket Xeon with Core i7 architecture.
A single-socket Core i7 machine has 4 CPU cores with hyperthreading:
each socket is THUS capable of running 8 threads simultaneously.
That should be enough for any software you want to throw at it,
particularly if you are only running one copy of your fluid dynamics model
at any given point in time.
Next decision is the clock speed of the Core i7: go for the fastest
because you've got plenty of budget for it, and it was just reported
on the Internet that all Intel Core i7 CPUs are "unlocked" --
meaning they can all be overclocked.
So, buy a motherboard that makes overclocking easy, e.g. ASUS P6T.
As for RAM, X58 chipsets now support either 12 or 24GB of DDR3 RAM:
look into Corsair's high-end Dominator series, with the memory module cooler.
Kingston make engineering samples of 4GB DIMMs x 6 = 24GB total e.g.:
http://www.hexus.net/content/item.php?item=17187
The Corsair power supplies w/ 850 Watts and up should be enough:
they are very highly regarded for high-end workstations like the
one you want to build:
http://www.newegg.com/Product/Product.aspx?Item=N82E16817139009&Tpk=N82E16817139009
I'll leave your graphics hardware choices up to your own good research.
If you are really serious about writing very large data files,
then be sure to give serious consideration to motherboards
and/or RAID controllers that can pump data quickly to and from
SAS (Serial Attached SCSI) hard drives: these come in both
10,000 and 15,000 rpm e.g. Seagate.
Despite what lots of amateurs claim, in ignorance,
a RAID 0 with multiple (4 x or 8 x) HDDs can really move a lot of raw data
very fast: 250-300MB/second is quite easy, and 500MB/second
is within reach, if you know what to buy and how to configure
your storage subsystem. The key is choosing a RAID controller
that does parity computations in hardware, e.g. Areca, 3Ware
or Highpoint's "enterprise" class controllers (there are others).
Out on the "bleeding" edge you will find Fusion-io's ioDrive Duo
(Google that one), or OCZ's new Z-drive (actually just a
Highpoint RocketRAID with 4 x OCZ MLC SSDs inside the
plastic shell).
Lastly, we've had enormous success with ramdisks
by installing RamDisk Plus from SuperSpeed, LLC
in Sudbury, Massachusetts: www.superspeed.com
A little bit of intelligent memory management, tailored
to your application software, can pay enormous dividends:
Core i7 memory bandwidth BEGINS at 25,000 MB/second
(25GB/second), and goes up from there when triple-channel
DDR3 is overclocked.
This is THE hottest computer hardware available
at the present time for workstation-class machines.
AMD still can't even come close.
hope this helps
MRFS