I got the Vortex Crossfire II Straightwall Cartridge BDC 3-9x, on a refurb Vortex Pro cantilever mount. I am a sucker for all things Vortex. They have been a great customer service company to deal with, and I like their optics.
I have one of their 1x prisms, and it is great on my Banshee. The 350 Legend upper is only for deer within 100m, so this should be more than enough glass. I really don't think I need anything more expensive, higher mag, or higher quality for an upper I might only shoot a few times per year.