Under #2, the cap upgrade probably gives the most performance gain.
One thing about the cap upgrade, the caps take up so much room, there is no room for an extra brace behind the woofer.
So if you go for the (internal) cap upgrade, you should also get the black hole.
If you get external XO's, this of course does not apply.
It should be noted the brace I'm talking about was not one originally designed in the HT3, but was going to be added at my request after a knuckle wrap test at AKfest. The cabinets are pretty solid as originally designed.
If I were to get the external XO's, I'd ask for this brace and BH5.