I have to many EQ plugins. Cant say my ears really can tell much difference.. Perhaps that says more about me, my setup and my ears than the plugins themselves. But Id say you get pretty far with cheaper plugins.
If Id throw away all my EQs and start from sqratch Im not even sure Id buy anything else than the bundled stuff that comes with Sonar. You shouldnt underestimate the ProChannel stuff.
But if Id buy anything it would be One of the below:
1. Meldaproductions AutodynamicEQ - Most features for the Buck and awesome sound. Constantly updated, lifetime support, fullscreen rezisable Gui, great licensing system. Just install on all machines you want. No irritating dongle or licencer.
2. Fabfilter ProQ 2 - Looks and sounds awesome with full screen support.
3. Waves Schepps - I just love this one and use it more or less all the time.