Play around with room treatments and with speaker positioning. Your M33 comes with Dirac room correction. Have you run it?
Do not start throwing money at cables and the like until you have optimized the features in your current system.
Also here is a "guide" for speaker setup.
http://www.cardas.com/room_setup_main.php
Al of of peddlers lurk these pages and will give you a sales pitch, steer clear of those guys.
- built-in Dirac Live room correction with included calibration microphone improves clarity and stereo imaging.