Get the correct specs from Eminence. The ebay seller's information is a mess. He lists two different Fs specs, and the Vas is all wrong for a 15" as well as the Mms.
Also, take inside measurements of the enclosure, especially with combos. Looks like you are including the area occupied by the head unit as well.
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The Vas and Qts are too high to use that speaker in a ported box that small.
The emi neo drivers are great in small boxes, but they can be cost prohibitive. Check out Faital Pro. I have a couple of their twelves and they rival the emis at half the cost.
It's likely as good as you're going to find affordably, models well down to 3cu.ft. at least. Most 15 combo enclosures are more sized for a 12 really and don't justify $200-$300 drivers. Compact/convenient takes precedence over better sound.