Anyone hear Vivid Audio Speakers? Considering Vivid Giya G1 Series 2 from Magico S5 MKII

Stick with Magico and work with the subs. If you cross at 100 Hz or above and put a high pass filter on the Magicos thingswill get much more dynamic. I have never used REL subs so I can not comment on them. Go to a store that has them and turn them up high with something like Jeff Beck's Loud Hailer on. Put your hand on the sub. A good sub you'll just feel a hint of vibration. If it is really buzzing away the enclosure is not built well. Ideally you should feel nothing. Very few subs can do that. Have you thought about the 15" Magico Q sub? It is actually a dual 
15" so you might get away with just one. 

No not for that money. I would just upgrade my speakers before spending that much on a Magico sub. Not sure why I would want to chop a full range speaker off at 100hz? I’ve never heard that before? Not even with bookshelf’s never mind a modern full range speaker? I’ll try it though because I’m always open to learning but the math certainly doesn’t seem to work though? 

One of the reasons I was disappointed when I auditioned the Magico A3 was a lack of drive and dynamics.  The A3s are spec'd at the same 4 ohm impedance as my Thiels, but with higher sensitivity.  And yet, even though the Magicos were driven with a higher current SS amp than my own amps, they sounded dynamically reticent vs my Thiels, or any number of other speakers I auditioned.    For me they did the "audiophile" trait of producing soundstaging and transparency and detail, but in a way that sort of just sat back behind the speakers.  They didn't reach out and grab me, or really "boogie" when asked to.

@prof 
My finding is the exact opposite of yours (I own the A3). The A3 DO NOT do the usual "audiophile" trait, and that is probably what you are missing (Your preferences seems to be of speakers with boosted highs/lows – almost like a loudness button, very common grab for audiophiles). The A3 are balanced, and like most Magico loudspeakers, super low on coloration, to some ears, this may be “boring”.