I've currently got the Crane Song Phoenix Iridescent plug-in running on my system at home and in Pro Tools 9. My computer is a Mac Book Pro that has a 2.2 Ghz Intel Core 2 Duo processor and 4 GB of RAM. I can't say that I've had any issues at all with this plug-in as my system is pretty stable in general and is able to handle almost everything I throw at it...
The Crane Song Phoenix Iridescent plug-in is one that every DAW owner should have, as the Phoenix bundle is probably the best when it comes to livening up a track to sound more realistic in a digital medium. The best way to do this is of course to use real analog gear, but as far as plug-ins go, these are the best that I've seen. Iridescent on it's own sounds awesome as it's great for adding some low end presence in there without over doing it. I like how easy the plug-in is to use as it makes it so you can pretty much throw it up and go. The others in the bundle are just as effective but offer up other colors. Phoenix is highly recommended for anyone who is working mostly inside the box.