Hi Matthew,
Maybe my experience will help since the measurements you give are exactly like mine; i'm also 5'7" and i also fluctuate quite a bit in weight depending on what type of weight training i do (i assume you mean something similar by "cycle", no?), usually 170-190.
I have the LCD 30 and SS plate, i've used it with a 3mm and a 5mm, with steel and aluminum tanks and i've had ample lift in all situations. Playing with that calculator linked above, the highest result it has given me in terms of lift required is about 20 lbs, even though the suggestions on lead are much higher than what i actually use. I'm mentioning this since it may also be applicable to you because of low body fat, but of course, no two people are exactly alike so take that with a grain of salt.
If i was to buy my rig from scratch, i'd buy the Torus 26.
Hope this helps.