You can do the same in Sonar as it has all the mastering tools you need.

Sound Forge has some tools that Sonar doesn't have and depending on the mastering job I prefer doing it in Sound Forge.

I recommend you got to the iZotope website and download their mastering guide. The information there is invaluable and while they talk about using ozone and other iZotope software the principles apply to all mastering and any other plugins that perform the same job.

When mastering I export a stereo final mix version into Sound Forge (11) but if I need to do some difficult kind of edit while tracking or mixing. Etc I will often just highlight the audio in Sonar and process it in Sound Forge. It provides a seamless workflow for me as it's just like Sonar has this audio editor on steroids right inside.

If you want a separate program for mastering Wavelab is ok. I find it a little wonky though and Steinberg can take their dongle and stuff it, so I'd recommend Sound Forge instead. It has a real nice user interface and workflow. Only real issue with it is the included effects are pretty much garbage. So you'll be wanting to provide your own VSTs. However do that, and it works well, including great batch processing. I don't have it at home, but I use it at work.

I use Wavelab 6 for wave editing and DSP. In a previous version (8.5 Producer) I was able to use Wavelab to edit clips in the Sonar project. I would select the clip, right click on, and it calls Wavelab and opens the file. I cannot remember how I got that to work from a menu in Sonar, but I think it was pretty simple. I don't think there was any registry editing involved. 
Can anyone help me get Wavelab 6 integrated with Sonar Platinum? Thanks in advance!
 

I have Soundforge 11 and have used it maybe once for noise reduction. I use Sonar for all mixing and all mastering. I may use Studio One 3 for mastering in the future. Not once have I used Soundforge for mastering. Today Sonar has too many tools for nearly anything one would want to do including mastering. I also have Ozone 7 Advanced. Plus a slew of other VSTs for mastering. 

hheine
I use Wavelab 6 for wave editing and DSP. In a previous version (8.5 Producer) I was able to use Wavelab to edit clips in the Sonar project. I would select the clip, right click on, and it calls Wavelab and opens the file. I cannot remember how I got that to work from a menu in Sonar, but I think it was pretty simple. I don't think there was any registry editing involved. 
Can anyone help me get Wavelab 6 integrated with Sonar Platinum? Thanks in advance!
 

Hi. Go to http://forum.cakewalk.com/SONAR-Resources-and-Utilities-m3392713.aspx#3472457
scroll down to Scook's Tools, and download SONARToolsEditor
All the best.

With SONAR Platinum and Wavelab 9 you can select clips in SONAR and open them via Utilities Menu in Wavelab. There you can edit or process each clip. By closing Wavelab the clips are send back to SONAR. Works perfect.
We use Wavelab Pro 9 for batch-editing in SONAR.
Also for pan-normalising and pitch-shifting.
The Editor from Wavelab is not better than from SONAR.
The included plugins from SONAR and Wavelab are a matter of taste. If you work with appropriate plugins (iZotope, UAD, Waves ...) SONAR has a better workflow (in my opinion). But the result is the same.

Old thread but glad someone found scooks tool editor  as its hard to find around here. 
 
I have used Wave Lab since  #4
I use elements 7 now and it's main attribute is you can global analyze your song to see what the average RMS level is. Sonar does not have that feature.  It's also way easier to top and tail songs and seek and destroy spikes. 
I find Wave lab does most editing tasks with fewer mouse clicks so for me i's faster and more efficient. 

I use Samplitude Pro X for mastering, it's VERY powerful. I still use SONAR for tracking and mixing, but that's just a preference issue because I've been using it since I bought it on a floppy from Greg Hendershott himself. Samplitude can handle the entire process end to end for those inclined to learn new tricks.