Nad M33 or something better

I most strongly doubt it’s the amp. Kef R3 have pretty good bass for their size and the m33 should be able to drive them to their max, but most any smaller monitor speaker can benefit by properly adding a subwoofer or two. In general larger rooms will always require larger speakers overall to deliver good quality full range bass. Subwoofers help achieve that, especially with smaller speakers.

I agree with @mapman. I would look at adding a subwoofer. 

Hey guys thanks for all the suggestions. As a matter of fact, I added a Kef KC62 sub yesterday. It made a nice improvement but stills needs some adjustments. I'm hoping this will solve the issue.

Thanks to all. 

Nice! Good choice on the sub!

I’m sure you will end up in a better place this way, but the key is to get teh sub dialed in just right. A good sound meter app like decibel on Iphone along with some streamed white noise as a reference signal can get teh job done fairly well.

FWIW I have KEF ls50metas and use a sub with those in a smaller room. I tune in the sub using the tools mentioned above and this makes a large very clear and noticeable difference. I do not use an active crossover to limit low end going to the mains, which would probably take things to an even higher level, but the results as is is still quite good. R3s are a step above ls50s in terms of their inherent ability to go loud (say above upper 80s db in a modest sized room) with low distortion, but playing things that loud is never good for your ears regardless so always be careful there.

Good luck!.

hegels are used by kef at shows, and i would suggest they do this for good reason, sonically....