Preamp Recommendation

Hi 
I have just purchased Classe CTM-600 Mono blocks. They are currently running with an old ML 38s. I have tried using a VTL 6.5 III but had a hum problem. Tried everything but could not get rid of the hum. The 6.5 was not new so the pre it self could have had problems. 
I have an option to buy an Ayre KX-R at a great price. Question is will the Ayre a significant upgrade on the ML? Speakers are B&W 800 D. Sources include Clear Audio TT and a PS Audio Directstream Junior. 
Thanks