Jimbo,
I've got about 25 or so Waves plugins as well as plugins from Eventide, Melda Productions and others. Waves have always been stable for me. Honestly, I've only been able to buy them when they were on sale, so with the Thanksgiving, Black Friday, Cyber Monday, etc. sales, I have been slowly building them up over time. Sometimes they are on sale for as low as $29 as well as offering a some of freebies for promotional purposes. I just picked up Trueverb this weekend as a free plug.
Now, as far as them being better than other plugins, including those offered by Cakewalk contained within the DAW, it is my opinion that they are not
significantly better than what comes with Sonar. Waves plugins certainly are equal to or
might exceed Sonar's
somewhat since they are a dedicated company that specializes in audio plugins and that's what they do. They do provide more variety of plugs overall if you're looking for certain plugins that Sonar doesn't offer, even though Sonar offers a lot. So, in brief, I do not believe that having Waves plugins are going to make or break your mixes. Plugins from other companies, such as Izotope, ToonTrack, etc. will also serve you and get the job done.
It sounds like the client wants you to process your audio at certain steps or levels in your mixes, either to fatten up, brighten, compress, etc. tracks or final mixes, including "mastering" before you send it out. You indicated that you have not been mixing very much until lately. Perhaps some folks here on the forum can help you with that. Either way, you got the most important part down: the Music! You just need some help with mixing I'm guessing.
Regards