Well obviously Logic Express is the next step up from Garageband, and a hefty step up; well worth the cost if you are making serious music. From Logic Express, there are many other choices, depending on your budget. Logic, DP, Pro Tools, etc.
I can without doubt recommend Ableton Live 5. Just head over to http://www.ableton.de and download the demo. It's great fun and was worth the money for me. Great software to do DJ sets, remixes and mash-ups. Oh, and some "serious" music making as well, of course.
If you double click on a track and then open up the "Details" checkbox you have two drop down menus after in the "Effects" bit after the "Compressor". In those drop downs is all sorts of stuff. A huge EQ with presets, plus simpler EQ's, you can click on the pencil icon to alter it fully manually.