You have a really nice set up going there. I think that the 6'8 MXF is the better choice. I'm not sure if you have seen the new Legend Elites but IMO they are better built than the Extreme's. They have the same blank (so same amazing sensitivity), have a beautiful full cork handle, and have absolutely amazing torzite guides (best guides I have ever seen/used on a bass rod), not to mention that the rod is as light as a feather. If you are curious about a Legend Elite something like an ES68MXF might be good to consider. However, the Legend Extreme is still a great rod and you will not be disappointed.
How big are the stripers in your lake? If they are in the 5-7 pound range I couldn't see a problem. But if they are the big ones in the 15-20lb+ range like the ones out west that gorge themselves on trout you will be underpowered.