Something to ponder over. Here are screen shots of a 48 track session with 10 Aux returns. The H/W buffer is at 64 with 18 tracks(The max physical inputs allowed in PT LE) ready to record from my 002 and Alesis AI-3!!
The Tracks.
The Aux Returns.
The Plug-Ins.
You will notice I am using some plug-ins that are quite the CPU hogs. AC2 and SSL Channel strip on the 48 mono tracks, 1 SSL comp on the Master Fader, and 4 Rverbs, 1 Dverb, 1 Waves Doubler, 4 Digi Extra Long Delays, 2 Digi 1 band, 1 Digi 4 band on the Aux Returns with about 25% CPU left over. And just for kicks, I routed the 18 tracks to the Hall reverb. And this is at a buffer of 64 with 25% CPU left!!
With a buffer of 1024, the CPU meter drops to 1/3rd.
Not bad for the 'slowest' Quad Opteron 265 we have out there, or what marspe would call the "Babyzilla". As you can see, you will probably have more power than you will use. Even in the 'slowest' Quads.
And by the way. I can attest that this Quad is 100% rock solid stable with no issues at all. Do you really need "the fastest" Quad?
The Opteron 265 gives us 134 Dverbs, Opteron 285 is 176 Dverbs and the MacIntel Xeon 2.6 with OSX is 190 Dverbs.
Very doubtful that you will max out any of those systems.
Hope that helps.
Shane