I agree with Jeff. There are great EQ plugs in Sonar, (some of which I use in every project) but they're not equivalent to IK's Master EQ 432. That thing does some kind of magic that no other EQ I've owned or used can do.
I bought it last year during their year end/Holiday/group buy, sale. I believe it's well worth the money. Even better if you can get it on sale.