X3 Pro has just about everything you need. Sonitus suite is good and basic and comes w/ everything. For comp and EQ the Prochannel has about as good as you are going to find. The SSL buss comp is superb. I would suggest getting the PC opto comp as a complementary comp for the PC Fet - it too is about as good as you are going to find. Perfect Space convolution reverb is, again, a great basic reverb, esp. once you collect extra impulses. Breverb finally fixes the hole in Cake's algorithmic reverb. It is great.
All those above provide your meat and potatoes FX and are high quality. The Nomad collection is gravy and fills the weak spots in Cake's normal delay collection. The Sonitus suite had delay, but wasn't necessarily intuitive. I already had the Nomad bundle but was still pleased Cake rounded out their FX w/ it.
So, if you have X3 Pro, you are set. Waves is good stuff and a lot of pros use it, but Waves keeps finding ways of getting your money. Change OS and you might have to buy everything of theirs again. UAD stuff is great - many pros swear by it, but their best stuff is "vintage" (which ain't a bad thing), but again, people end up buying more software and even worse, more DSP. Good stuff, if you have the money.
I've got both the Softube Mix bundle and the OVerloud VKFX bundle. Both are great and work in the PC as well as FX bin. The softube reverb was first stop before Breverb came along. The PC EQ is great, but the softube focusing EQ is a good one to have that is different. And the FET comp may be a hair better than Cakes, although neither one is as good as a hardware 1176 for spanking in a bass, guitar or snare. The Overloud keyboard fx is really great stuff and will expand your time-based fx about as far as you need. Better sound and faceplates and starting presets than the Sonitus stuff. The Overloud Bundle ($99 at the Cake store) is the first thing I'd look at to expand SONAR X3 Pro if you wanted more delays, etc. UAD if you want to mix vintage-sounding mixes, but you will be spending closer to a $1000 to get any kind of firepower and effects (or wish you would have).
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