Hold up JMG, that's not how parallel resistance is calculated. Total resistance in a parallel circuit is 1/(1/R + 1/R), so if the subs are 4 ohms and wired in parallel, it's 1/(1/4 + 1/4) = 2 ohms. Another thing to consider is that these subs are dual voice coil subs, meaning each coil on each sub presents the rated resistance and the individual sub can be ran with it's own coils wired in parallel. So if they are the 2 ohm version, here are your possible combinations:

1. Each sub can present either 1 or 4 ohms depending on how you connect each coil to the other one
2. Together, if they are both wired for 1 ohm, parallel would give you 1/2 ohm and series would give you 2 ohms
3. If they are both wired for 4 ohms, parallel would give you 2 ohms and series would give you 8 ohms

If they're the 4 ohm version:

1. Each sub can present 2 ohms or 8 ohms
2. Together, if they are both wired for 2 ohms, parallel would give you 1 ohm and series would give you 4 ohms
3. If they are both wired for 8 ohms, parallel would give you 4 ohms and series would give you 16 ohms

Clearly some of these options don't make sense in this application, but this should give you an idea. Essentially, the amp just sees one resistor in place of both subs. It's important to figure out what that resistor value is in order to understand the power that your amp can deliver.

Also, amps put out more power with decreased resistance, not the other way around as JMG said. Power=(Volts)^2/Resistance, and voltage is constant at a particular gain setting. All of these equations can be looked up online if you don't believe me.

Wiring is very important though. Not all wiring is created equal, even in the same AWG. There are two main types used in amplifier wiring, CCA and OFC. Copper clad aluminum (CCA) can't handle anywhere near what oxygen free copper (OFC) can simply because aluminum doesn't have anywhere near the ability to conduct that copper does. As with anything, there are varying qualities out there. Higher end manufacturers may oversize their wire while lower end ones may undersize theirs. KnuKonceptz is one brand that is known to oversize their wire substantially, and their CCA may outperform some of the cheaper brands OFC of the same AWG. If your amp really is putting out 1000W RMS, it may very well need 0 AWG wiring. It really has little to do with wattage, but rather the current draw of the individual amp. Smaller wire will melt the insulation off if you try to run too much current through it.

What amp are you using by the way?