I used the NHT 1259 for years and liked it's performance and sound
quality in my previous, small car.  Now moving up to a bigger car, I
thought about trying something different so began looking on the web to
see what is available.  I did a lot of T/S calculations lately!

Unfortunately, nothing I found can match the NHT 1259 low F3 (about 27
Hz) in a 2.5 cu-feet sealed enclosure.

Most have great excursions and power capability but ends up with dismal
F3 of in the 38 to 50 Hz range, unless equalization is to be used!

Is there something I missed here?  I know about cabin gain in cars but
still, 54 Hz F3 seems pretty high!

Here are what I have looked at so far (Qtc of 0.707, sealed)

Dayton Titanic 12 MK III       (F3=36 Hz @ 1.65 c-f)
Adire Shiva MK III             (F3=38 Hz @ 2.33 c-f)
Adire DPL12                    (F3=29 Hz @ 2.47 c-f)
Image dynamics IDmax D4 V.3    (F3=42 Hz @ 1.74 c-f)
Image dynamics IDQ12 D4 V.2    (F3-54 Hz @ 0.90 c-f)
Image dynamics ID12 D4 V.3     (F3=41 Hz @ 2.10 c-f)
HSU ASW1203                    (F3=42 Hz @ 1.73 c-f)

Of those, the Adire DPL12 have the best extension at the expense of a 3
dB loss of sensitivity compared to the NHT 1259.

I intend on having about 400 watts either on 2 or 4 ohms, available to
the single, sealed 12 inches sub, about 2 cu-f).

Opinions and help would be appreciated!