Really great bike, but too small for you IMO.
I am 5’11” and ride an 18″ but really I think I am ‘between’ their sizes: the 20″ would be too little standover for me, but for whatever reason, the top tube is an inch shorter on the soloist than it is on their geared xc frames and i have a 100mm stem on mine to make it feel stretchy enough for me.
If you have long body and arms and like a long reach you will feel well cramped on the 18″: it has only a 22.5″ top tube. According to the website even the 20″ has ‘only’ an 23″ top tube.
I would look out for an on-one inbred or scandal: much longer top tube in relation to seat tube length and also great fun to ride. T’wife has a slot-dropout inbred and frame weight is near enough the same as the white (ie not the 853) soloist.