Fabfilter's Saturn is excellent for this sort of thing on synths - it's a swiss army knife of very well modelled character and far, far more precise and useful than most of those simplified "tape" and "character" effects out there. Right now you can use it for free - they're extending the trial period indefinitely at the moment. Definitely watch their excellent tutorial videos (for Saturn 1 as well, it's much the same). Highly recommended. (Their Pro Q3 is also a superb EQ for helping shape and finesse your synth tones, but that's more focused on mixing than on character. I can't say enough great things about it, though.)
I also use Softube's Console 1 as a mixing aid and find it superb for warming up synths and helping fat patches sit nicely in the mix.
I prefer Saturn over Softube's own harmonics and tape plugins, but I find Console 1 to be just right for a mix bus - though it is much less precise in many ways, it is well designed for the 80% of the job that the desk is supposed to do, and it does that part well.
Edit: I also use RME as my front end, a mix of UCX and FF800 line inputs. Brilliant stuff.