In Sonar the levels are as high as I can go. Any more and the finished product comes out distorted. However, when I burn to CD and playback the volume of the whole disc is quieter than a normal album.
This has nothing to do with sample rates or 24 versus 32 versus 64 bits. As noted above, your ultimate format has to be 44.1KHz 16 bits in order to conform to CD standards.
I'm guessing you're using some other software to prepare the files for burning, such as CD Architect or Adobe Audition, or maybe a separate SONAR project. Can you explain your process for going from 64-bit 48KHz to a CD? Part of your problem may be that you're maximizing volume at the wrong stage in the process.
Understand that perceived volume depends on averages, not peaks. Ozone's role in all this is to raise the average volume while making sure the peaks are not excessive. We can advise you on how to accomplish that, but only if you describe the complete process. What comes out of SONAR initially? Is it 48/64? If so, how does it get to 44/16?