well first use the dmm to give us an idea of how much voltage your dropping. your not going to be measuring current, but DC voltage actually. set it to the one that has a V with a straight or dotted line over the top, not the one that has a squigly line.
also 2k @ 14.4 ohms usually wont happen either. most likely you arent even at 14.4v with everything off //content.invisioncic.com/y282845/emoticons/frown.gif.a3531fa0534503350665a1e957861287.gif . im at ~14v sometimes 13.9 or so with everything off with my electrical. now add some voltage drops AND impedance rise and your sending WAY less than 2k to what is a known inefficient as hell 2k watt rms subwoofer. im willing to bet if you put that hifonics on a bl or a q you would get a higher score due to increased efficiency.
as far as impedance rise goes. use test tones in increments of 5hz or so from say 30-60hz. plug a dmm into the speaker terminals on the sub amp. then put an ammeter around the speaker wire running to your subwoofer. play a 30hz test tone at medium volume. write down the voltage and the amperage. multiply V x A to get wattage and divide V by A to get the resistance. so this way youll see at what frequency your getting X ohms and XXXX ammount of power.