Same sub for both applications: Kenwood KFC-W3013PS 12" Performance Series 1200W Subwoofer

A friend of mine was running one of these in a prefab ported box(budget setup). Likely around 2cuft, tuned between 38-45hz(educated guess?) Was seeing about 300-350w.

He ended up blowing the sub about a year later. $30 sub, no big deal. Reason was likely mechanical. Bridging 2 channels off of a 4 channel with no subsonic filter(and I suppose if the tune of the enclosure was near 40hz, that leaves alot of room for the sub to bottom out down to 25hz)

So now I want him to experience a sealed setup for the first time. (2) of these 12's sealed and they will see 700w.

I assume the 2 12's sealed in 2.9cuft is going to be louder right? Twice the power and twice the cone area.