For 150 that's awesome :-)
The 40mm Plössl don't show more than a 30mm Plössl, as the 1.25" barrel & field-lens then limit what's possible. So the 32mm Plössl has the nicest apparent field of view. ( https://astronomy.tools/calculators/field_of_view/?fov[]=2|105|||1||&fov[]=2|327|||1||&fov[]=2|210|||1||&messier=31 )
what would work best
It's a bit like this, http://blog.pixelgiraffe.com/wp-content/uploads/2016/11/dobson8eyepieces1200.png
A 32mm Plössl costs under $18 if you're patient, if you want a tad more field. Sadly the XT6 does not have a 2" focuser for a larger field of view (http://blog.pixelgiraffe.com/wp-content/uploads/2016/06/overvieweyepiecesxt.png).
