Man, you shouldn't start thread by that title... Hey moskus!!!

We already got the big one down there...
Anyway, for your question...
is it simply eq and compression/ limiting with good effects
...and bunch of knowledge. Writing is as simple as write words on the papper. But no matter how good your pen, it's worthless if you don't know how to write, nor what to write
Or, are the untangibles that t-rack, ozone, or?, have that are special?
I believe each has their own advantage. Something like price, accuracy, user interface, features, easy of use, optional tools, etc. etc. (Not to mention bugs!

) If it's possible, then we can only suggest read which are most popular among them. Pick two or three. Download the demo and try which is better for you. Once you picked your like, consider the price. Look at your gears. It's neccesary because your thousand dollars plugins won't gives it's best performance on (say...) Creative SB Live! cards. It will be good, but not it's best. maybe you better spend bucks on average mastering program, and upgrade your weakest link on your audio path (for example soundcard , monitoring system, room treatment, etc). I guess you get the idea

Hope it helps.
FYI, SONAR is NOT suited for serious mastering work. It's audio and MIDI multitracking software, which has limited mastering features.

Jaymz