One thing you could try would be to flip box over with and put spacers on the bottom, so that it downfires. I drive a truck and i can tell you that downfiring sounds much better. Be sure to deaden under the sub box at the very least.
God i miss my 10" TDX i had running of an old school JBL 1200.1. Best setup i ever heard. Love the TDX as they get very loud and sound amazing. I had the older gray cone TDX, not the D9 model.
I picked up one of these running off a 250 watt Kenwood mono amp that was free. It's in my 2001 Sierra in a sealed box, and gets loud and sounds excellent.
For $55 these RE's subs would be very hard to beat imo.
RE REX10D4
did these sell? I had 1 10" original TDX off a JBL 1200.1 in a vented box tuned to 35hz about 7-8 years ago. Best sounding sub i've owned and plenty loud.