^^you mean two 8" subwoofers?
two 8" subwoofers hits the same as about a 12" but more on the side of JL's 13.5's.
plus you can plce one behin each seat, for a more equal feel and sound, instead of one 12" anywhere.
If I ever do a sound system again in a small truck I'd use two 8's.
-TD

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2002 Red Mazda B2300
Short Cab, Short Bed, Pioneer sound system:
DEH-P5100UB deck, dual USB/aux inputs, single CD, organic display, remote
4 TS-A6872R 40 watt nominal speakers
2 TS-SW2501S4 250 watt nominal 10" subwoofers