First, I want to say thank you to everyone on this board for helping me troubleshoot many of the questions that i had before i went out and bought my new system.

SO, i would like to share with all of you what i purchased and how well what did or did not work.

Computer:
Mac G5 Dual 1.8
OSX 10.3.9
2.5GB Viking RAM
OS 7200 RPM Drive
Audio/Samples 7200 RPM Drive
Dual Sony 19" LCD Monitors
MAudio Firewire Audiophile

Software:
Digital Performer 4.52
Mach Five 1.2
Kontakt 2.0.1
MX4 2.0
Sample Tank 2 XL
Audio Ease VST to MAS Wrapper
Recycle 2.0
Bias Peak 4.0
UAD Project Pack
UAD Precision Limiter

Here are my results and opinions:
1 - The Dual 1.8 G5 works wonderfully and seems to have enough CPU to continue to crank several instances of instruments and many stereo aux tracks while running real-time

PERFORMANCE:
My CPU overload test was:
23 UAD plugins (a master chain and 19 EX1s)
1 DP Master EQ
12 Stereo Aux for Drum Kit via K2 via VST to MAS Wrapper
3 Stereo Aux for Percussion via K2 via VST to MAS Wrapper
5 Stereo Aux for 5 instances of MX4
1 Drum Subgroup
1 Percussion Subgroup
1 2 Track Subgroup
1 Synth Subgroup
6 Tracks of sequenced MIDI

All the above while having each instrument instance visually opened ie all 5 instances of MX4 on the screen...

Hardware setting at 512 Buffer and 24bit / 48k
CPU runs about 95%

Purring like a baby...
2 instances of MX4 (bass and synth)
1 instance of MAch Five (drums)
Stereo out of Kontakt percussion (with 3 instruments)
6 UAD plugs ie Pultecs, 1176s, LA2s, PE
6 MIDI sequences
Hardware setting at 512 Buffer and 24bit / 44.1k
CPU runs about 30%

Other notes:- Digital Performer does support AU but DOES NOT support multiple outputs for Audio Units, only for MAS

- Audio Ease VST to MAS Wrapper works perfect on Sample Tank 2 but is buggy with Kontakt 2 (NI instruments do not play nicely within wrappers)

- Several instances of "tiny" UAD plugins will add more CPU host processing than if you use less high CPU UAD plugins

- Mach Five does not seem to import Kontakt 2 instruments although it imports Kontakt 1 instruments

- MX4 can not be routed directly to a mono aux, upon load DP will ask to clear the instrument instance as it is found missing, there are work arounds

- Most used UAD plugs include Pultec EQ, LA2, 1176 and Precision Limiter (PL sounds "rounder" than Waves L2)

- Kontakt 2 library DESTROYS Mach Five library in all aspects ie quality and quantity (M5= 4.5GB / K2 = 15GB)

Well, I hope this helps some of you out there. Overall, this sytem performs quite well and almost flawlessly. I have switched over from Sonar 3 on a PC running a P4 1.8 with 1GB RAM.