I've just talked with Christian.
The UM18-3-22 can be used in a ported box, but you need a beefy amp with a good damping factor to control it's motion. He has several clients using it in such cabinets with good results but not with Crown amps.
I have had a look at specs of the Crown amps. They have a borderline damping factor of >200 but they don't specify for what impedance. We have to assume it's the figure for an 8 ohm load as DF is directly proportional to impedance. This means a damping factor of only >100 at 4 ohms which won't guarantee a good transient response with the heavy moving mass.
However, you would definitely have a guarantee of a tight cone control with the QSC DCA 2422 with a rated power output of 2400W also when bridged. The QSC amp has a damping factor of over 500 which is halved at 4 ohms (>250) compared to one of only >100 for the Crown with the 4 ohm load. Christian is in agreement with me on this.
But the QSC which sells for over $1200 in the US is a lot more expensive than the Crown. If you don't want to spend that much more money on an amp, the solution would be to go for the RSS460HO-4 which is more suitable for a vented enclosure, and easier to control with a less powerful amp.
In a 7.5 cf cabinet, you would be able to get an F3 of 23Hz which I think is adequate and way better than performance in movie theaters, except for IMAX maybe.
Here, a bridged Crown XLS 2002 or even an XLS 1502 would be amply adequate to drive this sub.
The mini Marty enclosure may not be suitable as designed for the 460, because of different Thiele/Small parameters , but if you order from Solen, they will be pleased to give you the appropriate plan for a 7.5 cf vented cabinet.