2 12's? why? those kicker subs will hit wayyy too hard if you dont want loud. and being rated at 800rms per sub your going to need a hefty alternator. the amp required to run those subs are gunna blow that alrternator and battery within a couple months. and the amp you are going to need is going to cost a lot more than the subs themselves. you will also need some hefty gauge wiring, preferably 4 gauge and thats expensive too. i ran 2 10 inch alpine r's with a kicker amp and went though 2 alternators and 2 batteries while running a 15 farad cap. it was only pushing 650 rms to each sub. the amount of energy those subs will suck is going to make your subwoofers cut out because the alternator wont keep up. i hope you know what you are doing and not just deciding to show your friend up.
Was this setup in a 94+ Mustang or another vehicle? The Mustang alternators doubled in output starting in 94.