This 18" pro driver has only 6mm XMAX for a total displacement of slightly less (my estimate based on average cone dimensions) diplacement than the less expensive 12" Dayton Titanic MkII 1202 subwoofer driver with its 17mm XMAX.
The Dayton driver has a shipping weight of 20 lbs. -- not sure if you could purchase it for a reasonable price. Peerless has some decent 12" drivers widely available in Europe.
Based on VAS specs, which correlate with enclosure size, I'd expect the 18" Eminence to require an enclosure at least double the volume of the 12" Dayton driver.