OK - here's the update on what happened when I installed my VSL samples (approximately 300 gigs) on an external SSD (Oyen Digital's Minipro 512 GB) via Firewire 800 on my mid 2010 iMac (27 inch screen with i7 quad core processor and 32 GB ram with USB 2.0 and Firewire 800).
A little background - using my internal 7200 rpm HD, it took an average of 20 -25 minutes to load a DP file which contained an orchestra of virtual instruments including Dimension Strings. In addition, it took 5-10 more minutes of playing the piece through for all of the samples to finish loading via streaming. So a total of close to 30 minutes before I could really begin working on an orchestral piece like this. By the way - The Dimension Strings are what really added significant loading time in my opinion.
After moving the VSL samples over to the new external SSD and telling VSL's Directory Manager to look for them there, I opened the DP file. In 5 minutes, it was loaded. Furthermore, in less than a minute of playing the piece, the remainder of the samples had finished streaming. A huge improvement.
In addition, Paul at VSL advised me that once I had the Firewire 800 SSD installed, I should reduce the Default Preload on the VSL Instruments Pro Player from 32768 to 16384. Upon doing that, the VSL samples loaded even faster, taking only about 2 minutes to load and only a minute or so of playing the piece for the remainder of the samples to load.
So now that I have added the SSD via Firewire 800, I have gone from a 30 minute loading process to a mere 3 minutes. So for anyone else in the VSL family who has an old iMac and does not want to figure out how to break open their iMac and replace the internal HD with an internal SSD, this is the solution until you upgrade your Mac. It is working beautifully for me.