very quiet playback

I don't really have enough information yet to really do much of an analysis of your current issue with volume, but I thought I would toss out an idea to you.
 
If you were to pick up an upgrade copy of X3 - whatever flavor of it you would like, or be able to afford, you could install it on your computer and it would cheerfully and happily co-exist with your older version of Sonar.
 
All kinds of folks in the forums have multiple versions of Sonar installed, and can open each one as desired without disturbing any of the other Sonar installations present on their computer, and doing this works fine.
 
I have Sonar X1 Producer, X2 Producer, and X3 producer installed currently on my computer, and I can open any of them just fine, without causing any problems for the one I opened, or the other installed ones.
 
Sometimes, third-party things go away, from one version of Sonar to the next.  This happened from X2 to X3, with V-Vocal being dropped in X3 - and it was replaced with another product called Melodyne.  Since V-Vocal was installed in the base install of X2, X2 is needed to be kept on the computer in order to retain access to V-Vocal.  So, lots of folks kept X2, for that very reason, since they had projects that had V-Vocal in them, and they wanted to keep access to it.
 
I have a general rule of thumb I follow for myself, which is that I finish projects started with a version of Sonar, with the same version of Sonar, and start new projects in the newer version.  This is a choice I made for myself, not any requirement, but I simply never have problems opening older projects, because I always use the same Sonar version the older project was created in.
 
SOOOO, sorry for the lengthy speech that had nothing whatsoever to do with your issue - I just thought it was important that you were made aware that getting any new version of Sonar would not mean having to remove a prior version - they can all live nicely together on your computer, and they don't take up much room to do so. :)
 
As far as your volume issues go, I would like to see if I could help you figure this out, but to do so I would like you to supply a whole bunch of additional information, such as all of the relevant settings in Sonar, your Driver Mode, project details, Windows Default Audio Device, your Sonar project details, interface model and driver versions, firmware version of your audio interface, if you can find it, pretty much any information about your system that could be part of the audio setup and processing on your system.
 
Since others are not having this particular issue - there are no widely reported threads about this occurring on other folks's computers, this means it is likely something particular to your setup/settings, and therefore solvable.
 
In addition, is your Windows Update maintenance up to date?
 
Thanks - I look forward to trying to help you work through this issue, and will keep an eye out for your posting more information about your system and the various settings and such.
 
Bob Bone
 

Sorry I did not see the audio box in your post ( late at night) 
Your issue will probably be that your trying to use both, so yes disable your on board while testing. You may or may not be able to have it co-exist with the Presonus ASIO drivers.
Sonar really works best in the ASIO environment and rarely works well with on board sound drivers. 
Very few of us will have windows sounds enabled at all as they can be super loud when heard through studio monitors. 
Forget your laptops sound system, don't use it. Use the Audio Box for everything Sonar. 
You should be able to disable the Realtech in device manager and then turn it back on when your need it for other stuff. 
Your time master needs to be the audio box and ASIO and everything will be fine. 
And I too liked Sonar 6 when I used it, nothing wrong with that, I didn't know it was 64 bit so that's good news.