focurite has its liquid technology thingy, and theres duendo from SSL. but mainly these are the 3 major brands including TC to provide DSP power to their plug in.
OH i forget UAD!!!
i do now own any setups with these 4, but the UAD samples that i heard sounds good, you can go the UAD homepage to find out more about it.

whats best is that, you get all the plug in needed for mastering with the UAD.
if i am not wrong focusrite liquid technology is more to EQing only, duendo is an SSL plug in of their channel strip, and TC powercore had to be upgraded every now and then, thats if you want the latest plug in's offer from them.
UAD costing just a little more, offers all the plug in that you need, from EQ, to compression, and they got a neve EQ in it too. so do check them out
for me personally i would get UAD anytime

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nowadays, plug ins are more affordable compared to hardware processing, thats why everyone is going towards plug in's, however theres if your computer could handle all these pressure. DSP help ease the load of your computer of course, but i had no personal experience with them, therefore i might not be able to advise you in this case.
but UAD had a forum which might really help

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