you mentioned jlw3v3 in your initial post. i have one and they need 1.25 cubic feet sealed or so
at the top end of your budget of 300 and top end of your mounting depth 6.89 in
you can consider JL 10W6v3-D4
enclosure with only 0.55 cu. ft.
600rms 4ohm
Amazon.com: 10W6V2 10-Inch Subwoofer...