The other option I was considering was to just go with an 870 as it's the Honda Civic of shotties, higher capacity, well-known reliable platform, can be customized to suit my needs.. Put a decent red dot on it and go to town (or just stick with the ghostrings).
TRaTSeRiF... You really should research the game(s) of 3-gun first "if" that's what you intend to use your new shotgun in...
Capacity isn't the most important factor in a shotgun. As a match director/stage designer I can mitigate any advantage you think you might have with a high(er) capacity gun. ;-)
Just like many other games, 3-gun has divisions based upon the types of equipment used. Decide first what div. you want to shoot
then choose your gear, If you don't care what div. you're going to put in then sure go out and buy everything, but don't cry when because on ONE little feature your gun has you get bump'd say... Into "OPEN".
For example... At a TH3G match if you had that red dot on your shotgun and your rifle had a scope... You'd be in "OPEN"
If only your rifle was scoped you'd be in Tactical Optics div.
As for ghost rings... Been there done that. 'Got rid of them.
There's a shotgun technical section over at the Enos forum dedicated to 3-gun shotgun.
Check it out.
I think you'll notice there are one or two shotguns that dominate the 3-gun game. None have ghost rings, rails, breaching devices or other doo-dads bolted to 'em.