I'm not sure about shipping, but DIYSG buyout 15s look to be a good option.
Here's more info on them: Eminence 15 subwoofer and midbass information
Here's more info on them: Eminence 15 subwoofer and midbass information
I personally love sealed, and they're certainly the easiest enclosures to make, tend to be smallest, easy to tune with DSP or a LT, and are by far the most forgiving of miscalculations, but they're definitely not the best "bang for your buck" when it comes to output. That's ported all day long and twice on Sundays.
Chris
Could not agree more and all pointsI mean it really depends on your goals. I like sealed boxes. I also like multiple subwoofers for helping smooth response (and I like how they look!). Do you want a ton of output, or are you willing to trade some of that for placement flexibility etc. Room size, your amplifier and DSP choices also play a role here. There isn't a right answer, except all else equal ported will give you more output for a given driver. VBSS is a good design, I just love my sealed box collection.
Between those choices I'd personally rather the 4 boxes.
Chris