Dual processor PIII 866 versus single Pentium 1.4Ghz

[mdevin@ozemail.com.au]

This is not a debian specific question, but I know there are some
hardware experts out there that may be able to help me and I would much
appreciate it :-)

I am considering upgrading our server at work.  I don't fully appreciate
the performance advantage / disadvantages of dual processors and SCSI
hardisks.

Here is what I have been recommended to get:
2x Intel Pentium III 866 Mhz
Intel TUPELO (STL2) Motherboard Dual Processor capable
Adaptec AIC-7899 dual channel SCSI controller
2x 512 Mb Intel Certified ECC Registered Memory
2x Cheetah Seagate 36Gb LVD Hard Disks
+ network cards, floppy, CDROM, etc.

Basically, my question is:  What would the difference in performance be
between this configuration versus say a single P4 1.4Ghz?

This server will unfortunately have to run Windows NT (as the
proprietary software requires it).  It is basically a database server
with 8x 486s acting as essentially dumb terminals.  They will run a
basic version of the proprietary software and all the processing will be
done by the server.

1.  What do people think about whether it is worth spending the extra
money for dual processors?  Does Win NT fully utilise dual processors?
It is nearly $1500 (Aus) for the motherboard!  But a P4 1.4 GHz is much
the same price (I think), but the mother board would be cheaper then.

2.  Is it worth spending the extra money on a SCSI controller and hard
disks?

Here is what the specs say on the SCSI HD:
Formatted Capacity: 36.4GB
Interface: 68-pin
Ultra2/SCSI
Data Transfer Rates: 160MB/s
Average Seek Times: 5.4ms
Buffer Size: 16MB
Rotational Speed: 10000rpm
Height (inch/mm): LP (1.0/25.4)

Here is the specs on a 40Gb Western Digital IDE 7200 RPM:
WD CaviarTM 40GB EIDE Hard Drive WD400BB
Transfer mode: 100 MB/s
Average Read seek: 8.9ms

So the SCSI spins faster and has lower average access times.  I suppose
this means that it would be of benefit when you are talking about a
large database server with multiple terminals connected.

It is just hard to work all this out from the specs.  Can anyone speak
from experience on these issues?  Especially regarding the dual
processor versus single but faster processor.

Thanks for help.
Mark.