Weird issue...
 
I'm not sure how you ended up at 4096 samples buffer - I would put that down to 512 and look for other reasons to crackles, it's not buffersize that is the problem. Read somewhere, not sure if about ASIO or some other reason, but just increasing isn't better - and much dependent on drivers if it locks the cpu busses for all samples to be transferred, more samples over a certain limit may be worse.
 
Next thing I come to think of is if the loaded instruments you use - creating a fresh instance in Sonar - have the same settings for streaming from disk, preload i memory or whatever.
I would test freeze one synth at a time, and see which is inflicting the most.
 
Next thing - any antivirus software and Sonar should be excluded there. I run no antivirus at all at daw - but my working machine I tried 5-6 different ones, and all create more problems than any virus I dealt with.
As a test I would turn off antivirus completely - and that improve things look to exclude the Sonar process.
 
And finally, different graphics libraries may have issues, and Sonar might use another than Reaper - look for graphics drivers updates. And as a test - choose the performance setting(Control panel - System somewhere) in Windows if that changes anything, it will look dull for a bit - but just to narrow down.

precisionguided
The overclock is the first thing I'd look at for troubleshooting too, but for the fact that it wasn't problematic in either logic or reaper.

 
I honestly cannot see how you came to the conclusion that it will therefore not be problematic in Sonar.  Your system configuration is highly atypical; it's so far removed from my own that I have no idea what the cause might be and I have no means to try to replicate any aspect of your system other than OS and Application. 
 
However, given that my rather vanilla (and lower-specced) system runs Sonar, FL Studio and Studio One with no issues whatsoever, and has also successfully run fully-fledged demos of almost all other DAWs, it doesn't seem unreasonable to think that some aspect of what is atypical about your system is causing an interoperability issue with Sonar.  It's certain;y not a bad place to start looking.
 
Out of interest, what have you tried changing thus far to try to get Sonar working?

Good advice from lfm ^^^
 
You've got one thing going for you for troubleshooting, which is another DAW that does not appear to exhibit the same symptoms. They key is going to be finding out what's different. And by "different" I don't mean that they're different DAWs, but something else that's different between them.
 
That could be an antivirus program, for example. It could be re-scanning your .cwp file every time you make a change to it. Eliminate this possibility by *completely* disabling any antivirus software. If the problem goes away, configure the antivirus utility to excluded SONAR, the entire project directory tree, and the entire top-level folder where you keep your sample libraries.
 
I really don't think that Reaper is vastly more efficient than SONAR. Bear in mind that 95% of code execution time is spent in software external to the DAW itself: plugins, the audio interface driver, and Windows libraries. Efficiency differences between DAWs are therefore going to be very small. CPU usage will vary drastically, however, with different effects and soft synths.

If Reaper runs OK I can't see any reason why Sonar won't. I run Sonar at between 48 and 64 sample buffers without any problem at all. I have never had to set latency over 256 irrespective of the audio interface used, and I only needed buffers that high on an old P4 system. All things being equal, an i7 quadcore should produce good results.

A few other things to look at on top of the other suggestions.

If any of the cpu sleep states (CE1, 2 etc) are enabled in the BIOS try switching them all off, also any "turbo" features (oddly enough this can result in the cpu running at "turbo" speed all the time, but the cpu fluctuating is problematic in a DAW). If Windows cpu core parking is enabled, it's best disabled via the registry (I'm away from my DAW at the moment so I can't confirm the exact registry edit needed, but google should find it for you). Also make sure in the Windows power settings that the cpu is set to 100% minimum and maximum and all USB ports are set to "never sleep". The USB ports will also need to be told not to sleep in their properties dialogue in Windows device manager.

I use an SSD for audio spooling myself, though it's not RAIDed. RAID 0 in itself shouldn't cause any issue with Sonar, I used RAID 0 for years when I spooled audio to HDDs. It does need a scrupulous backup strategy though - I had three Seagate Barracudas fail within 18 months, all three while under warranty.

Thanks for all the help, guys. I found out that VST3 Antares plugins (in this case, harmony engine evo) don't play well with Sonar X3 and Plat, so I had to replace each instance with the VST2 version. Wow that bug caused me a lot of headaches.

Too bad I edited out the suggestion in my original post to start stripping out plugins; could have gotten there sooner.

Haha. Well at least I finally got there. Also, it would have been the last thing I'd wanted to do because I have way too many plugins to effectively troubleshoot. I just kinda found the solution by accident.

Double post

Haha. Well at least I finally got there. Also, it would have been the last thing I'd wanted to do because I have way too many plugins to effectively troubleshoot. I just kinda found the solution by accident.

Nice 1 :-)
 
Maybe there are some kinks in Sonar's VST3 implementation?  Its release certainly didn't meet with the warmest reception from the smaller plugin developers...
 
http://www.kvraudio.com/f...torder=asc&start=0
 
Oh dear!
 
I think I have less than a handful of plugins in the VST3/ folder, but I use v2.4 variants of those (and for all others).