OMG here we go again! 4+4 will give you 8 ohms, so the 520 brigded will NOT give you 520 watts only 260, change your sub to a dual 2 ohm and you will get 520 watts then. Please not you are looking at Max rating and not RMS rating, so you your sub will see less power than what they are posting.
the amp should have the top 25% power of the sub...in other words your sub is 1000W peak, so rule of thumb is look for an amp 750W and up...although you could prob. go down to 600 since this sub is 300W RMS