cleanness of the amp is of no worries when running subs. you will never hear the difference, same goes for the rca's you use. But back to your question, the hx2's are great subs, im thinking of getting 4 for my rig, the only problem is they are VERY power hungry. i would definitely save up for a rockford amp. The amp you should use is a BD110001 (1000.1 power series) tehy are a class d amp and put out around 1200 watts at 2 ohms. Keep in mind that while not needed you should also run a 1 farad cap to the amp. oh yeah, youll need 4 guage wire as well. but as far as saving up, since all the "new" 2002 gear is comming out you can get those amps dirt cheep (less than $460) if you were in wa I'd tell you to come see me and I would take care of you, but yoiu should be able to find them at 400 if you look hard enough.
As for ported box, they sound much louder in a ported box as compaired to sealed, but you do loose some sound wquality. all depends on how you listen to your music, if you like to play loud, go with a ported box MADE TO THE SPECS of the subs. that is what will make or break how they sound. if you run with the top off most of the time and you dont listen to rock, then you might want to consider a bandpass as well.
hope that helps, if you have any more ?'s feel free to ask
