Very nice! Of course, I'm kinda biased here because I have an Adire Rava, which is Adire's now discontinued pre-built subwoofer -- a 250W sealed design built around the same Shiva driver. (my BFD response curve is posted below) Judging from the 90 Hz crossover point, it sounds like we're also both using older Yamaha receivers.
Generally, a sealed box with the Shiva driver won't do much below 20 Hz, but I see that you've dialed in a +7 db boost at 20 Hz. Not sure if you want that because a +7 db at your listening position might create gut-churning boominess if you sit somewhere else. Also, that more gradual tapering off in the bass might subjectively sound more "musical" since that's a natural characteristic with sealed subs. Either way though, you're already doing well with your sub.
