I’ve been through the process of finding replacements for SOnar plugins for a while, following a decision to switch entirely to Macs and not being entirely happy with what comes with Logic.
So bearing in mind the VST may not be quite the same as the AU version of a plug:-
Cake’s 1176 comp - Waves CLA1176
CA-2A - Waves CLA-2A (Cakewalk’s emulation comes as an AU version which I have and in some ways prefer, but it’s tied to the Cake installer/authoriser so no idea how long it will last of course).
Concrete Limiter - Waves L2. d16’s Frontier is well worth a look as well, sounds very good but isn’t necessarily a good “last thing when mastering” plug.
Chorus/Phasing/Flanging/bit rate reduction - d16.
Delays - PGP Echo, Bozdigital Imperial.
Reverbs - Waves Abbey Road Plate, Valhalla, Eventide (all the Eventide stuff is excellent), Soundtoys LittlePlate (very good indeed at a lighter cpu load than the Waves Plate)..
Tape emulation - Waves Abbey Road J37.
Console emulation - Waves NLS is probably nearest equivalent to the Sonar PC one. There are also loads of complete channel-strip emulations around, other than ones with a strong character like the Waves Abbey Road stuff they tend to be similar as far as I can tell.
BozDigital’s +10dB is very good.
EQ - the Quadcurve eq’s emulation functions go beyond the “default eq” most DAWs have. Replacing that with something that has the emulation curves but also the graphical interface is tricky. I’ve ended up with a bunch of Neve/SSL and Pultec emulators but they do lack the number of bands and versatility of the Sonar one.
I guess I’m mostly using stuff from Waves, Bozdigital, Soundtoys and d16 overall. With Waves in particular I’ve been picking stuff up as it goes on sale at more sensible prices than the full price.
For a TH3 replacement all I can suggest is to get the full version. I don’t use amp emulators much and they’re very much a matter of personal taste as well so no suggestions there.