.7A means 700mA, and I don't think the guy really know what he is talking about... Your amp will not blow up by plugging in a higher current adaptor. But make sure you get a "regulated DC" adaptor, and make sure the voltage is equal or below 12V...

Have a look on your remote, there should be a button named "output" (can't remember exactly, cos I use a learnng remote instead). Pressing it should toggling between Speaker+H/P or H/P only.

Be patient! Before rush for amp, wait several weeks for E4's burn-in. E4 need much more time to warm-up.... A G5 ipod + E4 will not sound that bad...

I just get my E4s for a week, driven by my 3G ipod, I never get a problem of insufficient volume. Like gerG said, my volume never go higher than 60%.