Depends on what you want to achieve, you've got a nice spread of quality eyepieces there already
You might want to try removing the reducer sometime for views with your 11 and 9 at least, if you're interested in planetary viewing. Unless you have one of those rare invisible reducers, you're introducing extra glass and with the exception of the rare "Made in Japan" models the reducers have somewhat of a reputation for not necessarily improving the overall image quality. I'm trying to be gentle, but what's going through my mind is that you're not doing your scope justice by using the reducer all the time
With it removed, and on a good night, the 9 will show you more than the 11. The Naglers can be lovely and sharp at the native focal length in the C8. Unless you're out in the desert with excellent seeing, you're not going to benefit much from more magnification than that, if at all.
For pushing the widest FOV, stick the reducer on and the 16T5 should do a lovely job, but you can go wider with 2" eyepieces as Allan says. I use a 40mm SWA for example, good for about 1.35 degrees. I haven't -yet - tried that one with the reducer, but I'd expect the light drop off to be noticeable...but might be still worth a laugh
