I'm looking forward to buying the Alpine SWR-1021D subwoofer. My question is that if i got that what would be the best choice for an amp, i dont know how to choose one that will give me the best quality of sound. Also, i'm not even sure which i should get first the amp then the sub, or the sub then the amp. I'm new to this kind of thing so any info would be great thanks. Here is the type of sub i'm planning on gettting if everything works out:

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