amplifier wiring

so you hear hype about a 1 ohm or even .5 ohm system. but why does that crap matter? If your system is 2 ohms at 2000 watts or 1 ohm at 2000 watts, are they not the same? I'm curious because I'm deciding whether to buy the 2 ohm dual voice coil or 4 ohm dual voice coil version of the same...

I've done google searches, so I know re audio's recommended enclosures are too small, but I don't know just how big to make a sealed enclosure for it. should I just shoot as big as possible, say 8 cubes? I also know the rms rating is lower than what it can handle, but is that accurate for daily...

Achtung baby, I already have two sets of 8 gauge power/ground cables from my two previous systems. My new amplifier has an 90A fuse, so I'll definitely need a larger cable size. Can I just connect the two 8 gauge cable sets to the one amplifier? The combined copper should equal approx 2 gauge...