Hardware recommendations for 10,000+ part assemblies? Or...what is the bottleneck on my current machine?

Current specs:

Windows 7 Professional SP1 Build 7601

Dell Precision T3500

Intel Xeon W3550 @ 3.07GHz

12 GB Ram @ 533MHz DRAM Frequency

NVidia Quadro 2000

500 GB SATA HD

I ran the performance test and got these numbers:

Graphics - 93.2 sec

Processor - 139.7 sec

I/O - 132.0 sec

Overall - 365.0 sec

Rendering - 145.0 sec

RealView Performance 172.0 sec

I'm working on a plant that has over 20 tanks with multiple runs of piping connecting the tanks and structure around the tanks.  It's a pretty big assembly.  I'm trying to optimize my models for performance as much as possible.  I've tried: speedpak, supressing unneeded information, large assembly/light weight parts, and a few other things.  I can't help but think that my machine is causing some of my slow processing.

SolidworksGeneral