My freind is looking to get a up to 5000W RMS to run a 18" solo X. And he wants to know what would be a good amp for around 900 which might be hard. the 5000 is highly unlikley but he needs a lot of WRMS, hes looking into the Visonik V4000XD whichgives 4000WRMS for only 680 and free shipping. Since the website gives no details on it i was wondering is it a good amp? Or any other amps suggestions would be nice.