I have been using Xenon for quite a long time. A recommendation from
Danny Danzi here, I have always liked it. It can limit and add rms gain easily and mostly without destroying your mix in the process. It is a tweakable limiter and you can adjust quite a lot more than the average limiter. Putting it ahead in many ways. It sounds good and also has some interesting features such as longer term gain riding.
It can be used on tracks easily but on the main mix it does its duties well. It is excellent in a mastering situation. I like it when it is adding only 4 dB of rms volume increase. Taking a working -14 premaster into that loud -10 territory. It can certainly take it further than that and you can make very loud masters at -8. Or a more delicate use might be to set output ceilings and not add any rms gain at all. Just limiting only.