da5natch

so i currently have a 2011 impala with stock factory battery and alternator and i have 2 12in alpine type Rs about to be hooked up to an 8000 watt orion ztreet amp and also have a audiopipe eye candy with the audiopipe 1600w class d amp hooked up to it, ive got a good size capacitor my 5000 watt orion which is hooked up currently to the type Rs started cutting out due to low volts so i wanted another battery put in to help with power/light dimming/ overall sound quality. plus im upgrading to a higher power amp on one end so another battery is just needed since i cant really afford the time or money to get a bigger alternator, just wanted to know what are some good lower budget batteries that would be a good match for me the people doing the install suggested a marine battery, is that a good choice? or should i get better? does it matter if its a liquid battery or an agm battery? will a 12v battery be big enough? deep cycle i heard is what i want? i heard your not suppose to mix batteries idk this is why i need help lol any input is much appreciated. thanks.