what do you think about this tool as for mastering ?

G-Sonique - Mid-Side: stereophonic harmonic generator / vitaliser+

I haven't used this plug personally, but I imagine it's like all enhancer in that it's just what you need .5% of the time, the remaining 99.5%, it'll do more harm than good.

i've bought it.
Really good plugin.On some pretty centered songs can do wonders
in restoring the stereo image enhancing the side content.

try it!