For example, a 1,25x or 1,70 GPC on top of the 1,7x newtonian GPC with a Mark V binoviewer. That would give a nice flexibility.
The 1.7x is more flexible: It can be used with other star diagonals, too, as well as behind e.g. a Herschel Wedge for solar observation. It is also mounted the same way as the 1.2x, which may be more comfortable if you work with different glass path correctors to achieve several magnifications. That's why we usually recommend the 1.7x
Manufacturer Baader Planetarium SKU (#) 2456316 Weight (kg) 0.026 Outer Connection (eyepiece/-camera-sided) Barrel, Thread, M34, T-2 (M42 x 0,75) Magnification (x) 1 : 1,70 Optical length (mm) -65 Optical Design Glaspath Corrector compatible telescopes Refractors, Schmidt-Cassegrain, Newton