Yea-

This particular project I hope is going to be a great combination of digital and analog combined with sound physics and creative engineering, but I want to go in prepared to do battle...

...It seems your determined to have another conversation that I really am not interested in...

Just to clarify, I don't personally believe that Ableton has a sub-par summing bus but have heard this argumement over and over again and have some pretty creditable producer friends that also seem to think so. It's an interesting topic but I don't know I can't tell a difference in sound quality as long as your you're using warp modes correctly and using descent third party eq and dynamics plugins.
Now. Going back to the original topic, I fully agree with Kage's previous "psp vintage warmer is awsome" comment. If you've mixed your track correctly then you can literally throw psp vwarmer ontop of it and get Huge results with maybe just a little further value adjustments.

Also Aaron mentioned the Phatblaster in Reaktor which is pretty amazing as well, allthough I've always used it on drum buses and not on a full mix. But it does have a great sound and if yoy want to you can push it pretty hard.

What I'm using right now as my quick ableton "Go To" mastering chain is this:

Created an fx rack and stick two utility's (one on each level). Pan the 1st utility "Hard left" and 2nd utility "Hard Right". (this simulates hard plugging into two dedicated channels on a mixing desk and gives very nice results).
Created a 2nd fx chain and put the 1st one inside of it. Then, directly after the level containing the 1st fx chain, have placed "izotope ozone" followed by the "Wavearts final plug" limiter.
In ozone the only sections I have activated are the eq, the multiband harmonic exciter (with just the tiniest bit added to the low and low-mid bands), and the "stereo widener" (with a tiny bit of widening in the high mid and high bands).
I don't like ozone's maximizer so thats why I bypass it and use the "wavearts final plug" which, to my ears, is pretty transparent, light on the cpu, and can be really pushed hard before hearing noticeable artifacts.
The best thing about this is that youre able to save the whole thing as one fx rack preset for total recall in any other project.
I imagine that the PSP Vwarmer would be good to replace the Wavarts, although it's alot heavyier on the cpu (and since it has exciter-like features then you'd probably want to bypass ozone's exciter section).

to clarify on my previous post, i am not hating and i am *definitely* not flexing; i am pointing out that there seems to be a disproportionate amount of interest in mastering in pro audio forums, because i feel that this process contributes negligibly to the final product when compared to composition, sound design and arrangement, and mixing. assuming you are unwaveringly putting out bomb tracks and you have zero concerns from a song writing and performance perspective (and in all seriousness - who is?) if your final mix needs a stereo expander, that suggests a mixing (or recording) problem; if your final mix needs a master EQ, that suggests a mixing problem; likewise, it's not outrageous to say that a master compressor and/or maximizer can only be justified in light of the loudness war that's been taking place for the last few decades *at the expense of the final mix*.

(that being said, i use these tools, but their use is justified by my lack of skill!)

haha... Exactly!