A 6" f/5 is a nice finder in it's own right. Just add a Telrad/red-dot.

If you're looking for faint objects (faint in the scope) then you're not going to see them in a finder. A finder is used to position the scope between stars easily visible in the finder such that it is centered very near the faint object you hope to see in the scope. A wide true field of view often makes this easier.