Not all systems need a subwoofer. It really depends on whether or not your present speakers produce sufficient bass or whether you have acoustic problems with the low frequencies caused by the peculiarities of your listening room. If you do opt for the sort of help at the low end of the spectrum that a sub can provide, a good one can be had for a lot less than you are thinking of spending, and it should be fine for both music and movies. It's a myth that the two sorts of program make different demands on a subwoofer or any other speaker; a good one should be able to handle either.

One of the main advantages of a sub is that most of them contain their own amplifiers, which means the rest of the system doesn't have to deal with the watt-hungry bass. They usually have a selection of input options that allow you to drive them from the subwoofer output of an A/V receiver or from the speaker outputs (non-amplified, or passive, subs must be driven from the speaker terminals, of course). Some have low-pass filters that means only the bass is fed to the internal amplifier, but most A/V receivers and amps have that too, so it's not really critical. Magnetic shielding is only important if the sub is going to be placed within a couple of feet of the TV monitor, in which case it could disrupt the color.

No, as long as the connections are secure. Loose joints in any combination of wires can affect the sound. Otherwise, it's very unlikely that the material used in the wires would have any audible effect at all, although there are those who swear by things like oxygen-free copper cables and gold plugs. At least the gold won't corrode over time.

That would be the simplest way to compensate for the level differences that would be caused by the different sensitivities. But before you plunk down your hard cash for the new speaker, you should listen to the two side by side. The frequency responses may look the same, but with speakers these can be very unreliable guides, and the speakers might in fact sound very different. Just because they come from the same company doesn't mean they will necessarily match sonically.

That's one of the greatest uses of the VCR, as it produces about as good-quality analog recordings as you'll find, and tape speed is not really a factor, so you can make very long tapes for unattended playing, as you did in the past.

The procedures vary slightly from machine to machine, but there's no real trick to it. Whatever audio you feed to a hi-fi machine will be recorded both in hi-fi mode and in the much inferior linear mode, so you can play it on a non-hi-fi recorder.

Some older machines required a video signal to provide synchronization, even though you didn't have to watch it when listening to audio-only recordings, and that was most easily provided by the line outputs of a TV monitor. One correspondent told me he routinely recorded the cable news feed for this purpose, and used the clock at the bottom of the screen as a way to locate material on the tape in fast-wind mode.