Hi guys,  boy, what a learning curve this is!
I'm on a tight budget, but want the absolute best sound I can muster up for my mixes (or masters). All I have plug-in wise is what comes with Sonar Studio X3 /Producer 8...  the BC group, Nomad Factory stuff, LP-64 and misc, Lexicon Pantheon Reverb, and the stock Cakewalk and Sonitus offerings. Also a few stock 32-bit ones from Focusrite that came with the 2i2. And the Prochannel ones are there, too.
Since I don't have any other plug-ins to compare with, is there a decent package (or individuals) I could/should purchase that you would heartily recommend over the stock options I have? Something that I could go to and confidently know that it's doing its job very well, that many others are having very good success with ?

You can get stellar results with just the bundled plugins provided you know what you're doing with them.
 
Learn what you've got first then identify what you need.

what jonesy said - you already have the tools you need
good luck!

You don't say what kind of music you're mixing, but if it's the typical guitar, bass, keys, drums and other acoustics, I would suggest that you look at one of the following bundles (for mixing) from Waves. Their list price is ridiculous. I've purchased #1 and #2 below. In fact, I stupidly purchased #1 twice, so I have a second license I don't need and would be willing to sell you if Waves permits that sort of thing. More on that below.
 
#1 http://www.waves.com/bundles/chris-lord-alge-signature-series
#2 http://www.waves.com/bundles/eddie-kramer-signature-series
#3 http://www.waves.com/bundles/jack-joseph-puig-signature-series
#4 http://www.waves.com/bundles/tony-maserati-signature-series
 
I just started working on a test mix using the CLA and EK bundles. I need to clean up and gain stage the various instrument audio files (I'm using files provided by David Vignola of Vision Recording Studios in the July Quick Mixes instructional series ($9, btw)) and then I want to produce 5 mixes:
 
1) raw
2) with CLA in line (active) with all settings at default/unity
3) with each CLA plugin adjusted to my preference
4) with EK in line (active) with all settings at default/unity
5) with each EK plugin adjusted to my preference
 
It'll be a few days before I get through all of that, but this will be a nice, but simple use of Mix Recall.
 
Back to cost. Each of those Waves bundles lists for $500. Waves will often have one of them on sale (not at the moment, though) for $175. I managed to buy two licenses of the Chris Lord-Alge when they were under $100. Check out this behind-the-scenes story of the development of the CLA plugins.
 
http://www.waves.com/behind-the-chris-lord-alge-signature-series
 
I'm just starting on all of this and I want to see if a single instrument- or voice-specific plugin performs well enough for this noob. If you're interested in the CLA bundle, let me know. I'll sell my second license at my cost (assuming Waves supports that).
 
EDIT: A couple of responses posted while i was writing this. I agree with both of them. The reason I went down this path to start with was for a learning experience. Could I do all of what the CLA plugins, for example, do with the stock SPlat plugins? Sure. And I'll get there at some point. I don't know what your level of expertise is, so I assumed, for the purposes of my response, that it was similar to mine.

or if you really want to spend some budget money, check out toneboosters http://www.toneboosters.com/

I think you misread the OP Maartian. Your post is the complete opposite of what the OP is asking for. 

John
I think you misread the OP Maartian. Your post is the complete opposite of what the OP is asking for. 

 
I surely don't know how you came to that conclusion. Here's what I read in the OP.
 

Chevy
Since I don't have any other plug-ins to compare with, is there a decent package (or individuals) I could/should purchase that you would heartily recommend over the stock options I have? Something that I could go to and confidently know that it's doing its job very well, that many others are having very good success with ?

Waves are pricey even after their price reduction in the last couple of years. The OP states that he is on a tight budget. I would think this means that Waves are not a consideration. Melda free bundle may be more what the OP is looking for. Besides Bristol had already made the more important point about Sonar Platinum coming bundled with a whole slew of top quality plugins. I assume you meant well but if read the OP's post and title it is clear he is not looking for Waves plugins. 

I would say that you are set, with the tools you already have. Great music has been made with much less
Best of luck.

TheMaartianI surely don't know how you came to that conclusion. Here's what I read in the OP.

 
I think what John was alluding to and what you must surely have missed was the fact that the Op was asking for Economy plugs and you're suggesting the most overpriced bundles on the market, not to mention ilok. If waves are economy what the hell do you call expensive pro plugs?
 
Waves, (as you pointed out) are ridiculously priced.
 
I would suggest the OP steers well clear of waves and takes the advice of Bristol_Jonesey and pwalpwal and gets to know how to get the best from what he has because what he has can do a pretty good job and the are oodles a tutorials from cakewalk about mixing and mastering.
 
Maybe if he feels he wants to spend some more money for that extra polish something like Izotopes Ozone would be worth looking at as an all in one solution.
 
 
Steve