in TDM the Bombfactory stuff plus the Line-6 Echo farm (their famous green delay pedal) rules for guitar. While the Line-6 Amp farm is not in the same league.
As a universal multifx-unit WaveMechanic's Time- and Pitchfactory are outstanding, it's basically an Eventide (or rather multiple...) in a box. Same developers of the algorithms.
Dynamics Bundle by Drawmer and the LA2A/1176 by Bombfactory for compression.
For EQ I like the one by TC Electronics, for reverb the Lexiverb (often dissed, but cool) and RealVerb by Kind of Loud.
There are more of course, but I'd consider those mentioned essential classics, still valid today.
For the OSX machine it's clearly Scuffham's S-Gear in the guitar domain, it outperforms all the others mentioned and I doubt there's any native stuff in PT to compete.
I know someone who sold his Kemper amp for S-Gear because he didn't need it anymore.
TDM is history - Digidesign doesn't exist anymore and Avid doesn't care. The goodies are all downloadable for free. Most dongle licenses are very unlikely to run under OS9.
I sometimes considered this 'neat and clean way' myself... but then: it doesn't help the original developers anyway and the cease of support literally rendered gear for big $ useless.
So I just stopped worrying... and learned to love the ...