Well... STEAM EDITION installed!
Good news: working fine, read my old plugins (dx and vst)*, nice visual interface, price out of this world (little more than 4 dollars...) and my old SONAR X3 Studio not affected at all (both can be used), although I didn't notice any difference (new plugins or visual additions) to it.
* some plugins, though, seems to be "exclusive" to X3 Studio (some prochannel stuff, maybe).
That's it! Thanks again!
EDIT: more good news: I managed to insert Rapture Session and TH3 in X3 Studio, just by put their path on the plugins setup page and rescan. Rapture seems functional, but TH3 is demo.
EDIT: well... and now... some
BAD NEWS... File-Export-Audio is not working on X3 Studio... (in Steam Edition is OK).