Boom, as Michael pointed out, the internet direct sales process offers value to the consumer. If sold in typical stores the "suggested retail price" would be considerably higher.
As Rick's link showed, the ohm(honoring Dr.Ohm's pioneering research)measures the amount of opposition a wire, etc. offers to the transfer of electricity. Receiver/amps don't operate only at a specific ohm number, but since when the speaker has a lower impedance in ohms more current flows for a given amount of power, and this causes more heat in the amp, many units don't attempt to pass the tests required by the FTC and UL for official certification at 4 ohms, and are "8 ohm" units. Nevertheless, many units not officially rated for operation at 4 ohms can and do drive 4 ohm speakers well unless extremely high power levels are involved.
The answer to your question about your 4200 is probably yes(Axioms are about average, or slightly higher, in sensitivity), but you have to try it in your specific circumstances(room size, distance of listeners, average listening level, dynamic range of program material, etc.)to know for sure if it's satisfactory. Your speakers will use about 1 watt at a comfortably loud average level, but brief peaks will use much more. That could be 50 watts in many cases or 500 watts or more in extreme cases.
