I think C6 is the only Waves plug I couldn't do without. In my opinion, almost of their other plugs (at least the ones I can think of) have competing counterparts that do the job better.
EQ - DMG Audio EQuilibrium
Mix Compressor (SSL style) - Cytomic The Glue, SSL Duende
Mix Compressor (Neve style) - UAD 33609
Channel Compressor - UAD 1176/LA2A/etc.
Channel Strip (SSL style) - SSL Duende or UAD SSL
Channel Strip (Neve style) - UAD 88RS
EQ (Pultec style) - UAD Pultec
Modulation/Effects - Soundtoys
Harmonic Distortion - Soundtoys Decapitator, Kush UBK-1, Slate VCC
Tape - Slate VTM, UAD Studer/Ampex, Massey Tapehead
Reverb - Audioease Altiverb, Lexicon PCM Bundle, EastWest Spaces, Valhalla, etc.
Stereo Widener - Dr. MS
I know I'm leaving some categories out but you get the idea.
Personally, I'd invest in a UAD card over a Waves Bundle.