ok im purchasing a JBL BP600.1 amp for my subs. i can find it NEW online for 175$. i have seen many of them on auction websites for around 150$ but they have all been used for a few months. would this matter? one claims to be used for 5months powering a single alpine 12" type R sub, and another says it powered a single rocford for 3 days..what should i do? new or used?