The Kove KMG-X Was a Great woofer when it was released. These subs were originally produced as an OEM by Atomic for Kove. Later production was moved around and the subs were produced by other companies. The Armageddon was based off the same high excursion technology utilized in the Ground Zero and Orion HCCA woofers. The cones, spiders, and coils are interchangeable with the only the magnet structure size affecting the BL of the driver.
In the long term, the FI woofer will be the better choice as they are current production and supported by the manufacturer. It would be very hard for you to find support for your Kove as they have gone out of business long ago.