Sonitus is very old...had already them in sonar 5 if i remember well.it should be as old as pro tools 6 which was ugly too.
So,yes, GUI is old fashioned,but it sound quite well and is very very easy to use.Also,it's very CPU friendly.
When eqing tracks in console,default eq is the sonitus one until you switch on quadcurve prochannel.
Not flashy,but a nice and effective eq.
You can use toneboosters.com eq..it's cheap,sound great,has spectrum analyzer and is very very close to x3 quadcurve