For cheap SQ subs, you really can't beat Alpine.....The K's sound nice but I still wouldn't say they sound better than the type R in the SQ department. You might consider a single sub setup and give a type R or something similar the full 250w in the largest sealed box you can fit (within the driver's perimeters of course). Big boxes have great low end extention, meaning you'll get that teeth-rattling bass you normally wouldn't get with a small sealed box. It probably wouldn't be louder than a pair of subs on 125w each, but it certainly would have a lot more frequency range and would probably give you the bump you're looking for.
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