I have a PCI UAD-1 and the following plugins :-
LA2A, 1176LN, 1176SE, Fairchild, Putec & Pro, The CS-1 (obviously), Plate140, Dreamverb, Cambridge EQ, Nigel etc
As I don't have much DSP I stick to the plugs above and don't worry too much about lusting for a Neve console in my studio. For me, the Pultec's, Cambridge and LA2A are the foundations of my mixing and I can easily run a project with just one card. I also use the Plate140 a lot for reverb which if you like quality verbs, at least demo it.
I don't use the 'full' 1176LN much as the sub range gets smeared and lost by it which interestingly doesn't happen with the SE version. Use the SE for full mixes or low bass imo.
Fairchild is nice but you really need to understand how to use it. Again, I think it robs a touch of low end so bear that in mind but over a drum buss it can work wonders. Over at the UADforums there are some good stickies with some ideas and techniques to try out which sort of sets you up mentally for its uses and non uses as imo it can't always be used. Sorry if that sounds vague but when you use it like other compressors, its hard to hear anything magic but used correctly in the right context/material etc it will sound awesome.
Pultec's are stupid EQ's imo but I mean that in the highest regard. I challenge anyone to make the sound thru it worse than without it!!!! You can't, no matter how much you boost or where, it always sounds better to my ears. The amount of boost you can apply is scary and it stays musical.
Cambridge has a clean sound but the filters are the shit. Cleaning up tracks in a project is a joy and the amount of slopes available mean you can always find the right blend.
I have used the Precision series in demo and they are very good but I didn't buy as mastering is for others
Anyway, just a few of my humble opinions on the very wonderful world of UAD

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