For mastering, I find the Sonar plugs don't get me where I need to be. It can be done and I've done it before, but the ones you see that I use, do what I need to be done better in my opinion.
Just a quick example of why those are there and what I find wrong in Cake plugs that do the same thing.
I love that LP 64 eq for high passing and low passing. That's all it does. Nothing in my opinion handles things the way it seems to. And it sounds great and now that the Bakers have fixed the glitches in it, it's a breath of fresh air to use.
There are 3 Roger Nichols eq's that you see there. The reason there are 3 is because you can customize them to have as many bands as you want as well as pick the bands and settings you want. It's one of the most powerful eq's I've ever used for both sound and flexibility. Nothing else I've tried tops them. I use three because I have one dedicated eq for lows to low mids, one for medium mids to mid-mids, and one for high mids to high-highs. This allows me to instanlty control a frequency that needs to be controlled without having to constantly scroll through or create new bands. Each eq has like 14 different band settings and if I need to scroll through some bands, chances are I'm close to a band that needs to be controlled.
Next is my API compressor. I use this because it's simply one of the best mastering compressors I've ever used in plugin format. It's so versatile, transparent and loaded with options, you can't wreck a mix with it. Though I like the Sonitus compressor and all the other Cake compressors we're given, something about this particular compressor just speaks to me in how it deal with audio. In the mastering realm, I just want it to control all the little peaks and valleys I may have created with the eq's. This also keeps the mix a little tighter without artifacts.
From there, I like to run my UAD Multiband. This thing is so incredible, I've never used anything else that comes close. It's the perfect "policeman" for mastering as it will just gently push the crowd back off the line if they try to push forward. It is also transparent and near impossible for it to ruin a mix. The Sonar multiband is also good...but it works a bit differently than this does and starts to get artifacts where this never does.
Once all that is where I want it, I like to increase the level of the mix yet still keep it tight. This is where the Waves LL3 comes in. I just use it subtely without going over -2dB at this point. The audio I'm mastering was already pre-leveled manually and cured of all rogue peaks in my pre-mastering session, so using a little bit of the LL3 here just keeps things tight as we raise the volume just a bit. I could probably use the Concrete Limiter to do what the LL 3 is doing here. However, I find the CL is not quite what I like to use in a real mastering situation. Waves to me just has a handle on this a little better for me...which is just a personal preference.
From there, there's a Waves S-1. The S-1 only gets used if I seem to get a little stereo field smearing from the processing I've done. It's rare for me to use this as I never over-process to where the stereo field has been narrowed up. Sometimes though, a client may mix a bit too tight...so a gentle bump in the width here by like 110-120 may be the fix and allow things to spread just a bit. I could use the Sonitus Phase plug in place of this. But I prefer the graphic look of the S-1. They both do about the same thing really.
From there, the Waves L2 goes on and I kick the mix in the butt. I don't actually use it here though because I will use it in Wave Lab to finalize everything. But I will kick it on to see what I'm getting at this point. I use the L-2 or a PSP Xenon which is really nice. The Xenon can be a bit too clean for hard rock or metal though, so the L-2 is the better choice for me. Boost 11 and the Concrete Limiter choke when used passed -6.0 threshold. They just don't hold up and distort where the Waves maximizers give you much more output before they start to crap out on you in my opinion. The L-2 is great for 24 bit stuff...the L-1 and L-3 seem to do better with 16 bit.
After that is the Waves PAZ analyzer so I see what things look like. I don't rely on what I see as much as what I hear, but it's also nice to keep a nice eq curve in mind. I'll use this or the Blue Cat analyzer. To me, they give me what I need to see in a seconds glance as well as no mistake in the frequencies I'm looking at. And they are big enough to see at all times. So though we can definitely use alternative plugs, these are the reasons I use what I use on this end. :) Hope that explains it brother.
-Danny