A couple things to consider:
Many states have magazine restrictions when hunting. If yours is one of them you'll have to plug the magazine tube, which means an extended tube just adds useless weight. (Unless you're going to use it for HD as well)
Turkey hunting isn't duck hunting. Again, I'm sure it varies by state, but in Michigan I think the most tags you can get is two (one spring, one fall - in my area only spring). If I fire more than 2 turkey loads a year I'm doing it wrong, so recoil isn't an issue.
I would probably echo the 1187 sentiment, although a ton of turkeys have been taken with a basic 870 pump.