I have an all ARC system. That is my personal favorite with Wilson speakers. I have also had the ARC Ref 40 in house with the D’Agostino Momentum stereo amp which sounded fabulous. I believe ARC pres and Dag amps are a very popular combination. Check out the virtual systems of Dag owners here and you will see that when they want tubes in the mix, it’s usually ARC.
However, I have heard all of these brands and each sounds great but each has a different "house sound". It will all come down to personal preference. I believe all would sound great with Thiels which are also very revealing but musical. I suggest that you ask people with Thiel speakers or dealers who sell Thiel. Lastly, some manufacturers will give you some guidance if you press them. Or at least they may tell you the leading brands that their customers often purchase. My guess is that ARC and VTL lead the pack in sales but that doesn’t mean they will be best for you. They are radically different sounding although neither is "colored". They simply project sound in a different way.
However, I have heard all of these brands and each sounds great but each has a different "house sound". It will all come down to personal preference. I believe all would sound great with Thiels which are also very revealing but musical. I suggest that you ask people with Thiel speakers or dealers who sell Thiel. Lastly, some manufacturers will give you some guidance if you press them. Or at least they may tell you the leading brands that their customers often purchase. My guess is that ARC and VTL lead the pack in sales but that doesn’t mean they will be best for you. They are radically different sounding although neither is "colored". They simply project sound in a different way.