You can't bridge a 1-channel BUT it is 2-ohm stable.That means you can hook two subs IF they equal a 2-ohm load together.It will do 1k watts 4-ohm or 2-ohm.It's a nice amp but friggin pricey.
Which Alpine subs do you have?
I'm going to ASSUME you have the 10" marine by the 300 watt rating you speak of.If that is the case then they are SVC 4-ohm and both together will give a 2-ohm load.Basically both pos wires to the + on the amp and the both neg to the - of the amp.If you are putting 1k watts to both of these you are over driving them.300 each is about it for them.I have one in my boat with about 300 to it.
How do you know they went bad?
Usually you burn a coil up and the sub gets crunchy or locks up.