just thought I'd drop a note that I've come up with some reasonably clean/loud/sparkling results using the following:

various compression of bass and drum tracks or channels. occasionally using Classic Compressor with drums preset on percussive parts that weren't strictly drums -- and those changes required resetting some volume levels for pads etc. as there's some gain on drums

and at the master output
Classic Compressor with premastering preset tweaked a bit but basically threshold at -8 db, 2:1 compression (if anything I might turn that down a little), soft knee, no gain -- then

Ruby Tube with shaping preset 'Medium Sparkle' -- occasionally tweaked up or down slightly -- then

endorphin with preset deep m/s compression

and Vintage Meter to adjust master volume

Ruby Tube and endorphin really work well together, imho.

I tried demo versions of Voxengo's toolset with EQ, Lampthruster and Elephant. I'm sure I could squeeze a little more presence onto the CD with these tools. I esp. like the EQ curve. I'll be picking these up someday I'm sure. But for now, and for free, for the first time since I started fooling with mastering tools (all of a week ago or so -- 6 CD burn sessions -- lots of listening), I'm pleased. The real proof for me is it sounds good on the sound system a room or two away from the speakers.

Do you have some WAV examples, pre and post mastering ? MP3 is no good when you've been limiting your output, since it'll produce clipping upon decoding.

5-10 seconds, compressed with Flac or MonkeysAudio (lossless compressors) should do, if you decide to put up a cut.

i don't have a web site and so can't post files. I would suggest just trying out the combination for yourself. This is simply a suggestion I found usable. Playing with the PSP Vintage Warmer and Voxengo tools also gave me a much better notion of what mastering can and can't do.

Also I read an old two part article on compression and limiting in the online archives of 'Computer Music' and it turns out it's more standard practice to apply the 'amp warmer' to the signal prior to compression, so the chain should probably be
Ruby Tube, Classic Compressor, endorphin.
of the three Classic Compressor at the premastering preset has the least effect, but still it adds some coherence.
The amp warmer seems to have an effect that borrows a little from a limiter and a little from an eq shaper.

And I did have one production where I mis-assigned some instruments to the same channel as a double bass line -- so now I do know what pumping sounds like. When the compression kicked in on the double bass it was a very noticeable effect on the other instruments -- somewhat similar to a sudden reduction in pressure -- which in terms of sound physics is probably what it is.
Controlling and shaping sound pressure seems to be a pretty accurate analogy for the whole mastering topic.