Ok...well because this is still being somewhat debated...I dug into it a little further...though keep in mind this info may not be 100% accurate because there are things to factor in...and I'm not sure that the rating was for a multistrand copper wire...but this should get you pretty close.
Your amp (Profile ap2000) is rated:
» 960 W x 1 RMS bridged @ 4 ohms
» 480 Wx 2 RMS @ 2 ohms
» 320 W x 2 RMS @ 4 ohms
Your subs (Sony xplode 12" P5) have a 4ohm SVC.
The wire size you need is determined by the amperage being drawn through it. So you gotta get to that number... the calculation being Amp= the square root of watts/ohms.
So in your case...(and this is assuming you'll wire up the subs in stereo at a 4ohm load...I say that because your amp is rated 2ohm stereo/4ohm bridged and with those subs the only way not to draw too big of a load is to wire it up stereo) ....so your 320 watts rms/4ohm = 80....the square root of that is ~8.9 amps.
a 14ga wire is rated at ~32amp max load...so you should be just fine.
(on a side note...with that calculation even if you had 1000watts per sub at a 2ohm load you'd be at 22.36 amps...still fine for a 14ga wire)
Now could you go with 10ga sure...but once you already exceed the amperage requirements there is absolutely no benefit...why waste the money?
If I am wrong someone please correct me...was trying to take a stab and figuring this out mathematically...but it's been several years since I got outta college and this isn't the type of stuff I do everyday for a living..