helfen, ein 10 - Zoll-Subwoofer zu bauen

possibly it's better to write in english than use a translator

- Mivoc AW3000 isn't a 10-inch chassis, it' a 12-inch (30cm =12in ; 25cm = 10in ; 2,54cm = 1in)
- This chassis is made/designed for home-use. You can't build up a PA-system with it, it's not loud enough.
- Also it's not tough/robust/strong enough to survive the hard work a real PA-chassis/Subwoofer has to do.
- Your amplifier seems to fit for small setups. 200W/8 Ohms isn't very much. Especially for subwoofer-use.

If you need a Cheap 12-inch chassis look for Eminence Delta 12 LF A. Here in GER it's available from ~100 EUR.
SPL will raise and cut-off-frequency lower when you take a Eminence Kappa 15 LF A or a Kappa Pro 15 LF A. But these are more expensive.
There are many enclosure-examples for each of these chassis available on the internet.

I would, if i had these components, use dem Gemini Amp in Bridge-Mode with the Delta-/Kappa-Chassis.

Greetings