This is a custom enclosure I had made in the past for another customer. I would be happy to make you something similat to this if you would like. Please feel free to contact me for a quote.
This one used four Savard Hi-Q 6.5” subwoofers. The subwoofers are brand new have only been loaded into the enclosure and wired up. Enclosure is 1.75 cubic feet tuned to 35hz with a double 2” aero port. Wired with 12g ofc speaker wire through a pair of terminal bolts, one pair of bolts for each pair of subwoofers. They measure 4 ohms at each terminal bolt. There are two pairs of bolts so you would have a 2 ohm final load for a mono block amp.
These Savard Hi-Q 6.5" Subwoofers handle 350watts RMS each for a combined 1400watt RMS power handling. The special thing about these subs though is that they do not need the full 1400watts RMS they will work just find on any amount of power between 600watts-1400watts.
Underseat enclosure for 2015 Chevy pickup
For the Hi-Q 6.5" subwoofers.
https://www.savardspeakersystems.com/copy-of-hi-q-6-5