A:AnswerIt's better to have a little bit more power on the amp then you turn down the gain. For the price it is good for your 8inch but you can go down in power sure and still be ok.
A:AnswerYes, this amp would power both of your subs. This amp will run 2 600RMS subs. You will just need to ensure that you do not turn the amp all the way up so that you do not blow the subs since they are under the RMS of the Amp.
A:AnswerYeah it is but you would know because they would smell really burnt also you would see smoke. I think maybe just a wire got disconnected from your Alpine install, also it is posable to blow your 12 with this amp. If the Amp was set all the way up and you played constaint bass notes for like more than five minutes maybe.