Avoiding Emotiva seems to be the verdict. I hear of constant quality control issues. Sure, they might repair it for you under the warranty, but who wants to buy something anticipating of repairing it. Also, what happens once it's out of warranty? I guess you would be out of luck at that point.
The D-Sonic stuff looks like it's got potential, although a bit salty for me (very nice on the form factor though). I would prefer go with something from Behringer, like the EP2500 for lots of power. Honestly the SC-07 should be enough power for those speakers. They are moderately efficient and probably spend most of their time above 6 ohms (they have a nominal rating of 8 ohms). I honestly don't think you need an amplifier, as the one in the Pioneer is very solid.
Actually those speakers are a difficult load. Below 350 Hz, and that is the region that provides around 50% of the acoustic power, the impedance is 3 ohms. The speakers are nearer 8 ohms above 350 Hz. So if you calculate it out, roughly two thirds of the power will go to the lower three bass drivers. So the speaker is much nearer a 3 ohm speaker than an 8 ohm one. You would expect this with three drivers all paralleled below 350 Hz.
As an aside the sensitivity is misleading. There are two ways of specifying sensitivity. One is to specify the spl, at one meter with a watt of input. The other is to specify the spl. with an input voltage of 2.83 volts at 1 meter.
Now at 8 ohms the numerical value is identical. However your speakers are rated at 90db 2.83 volts one meter. Now this means that 1 watt of power will produce 90db at 1 meter above 350 Hz, but will require 2.7 watts to produce 90db at 1 meter below 350 Hz, almost three times the power.
Now the phase angles are not specified, but as a rule of thumb the current demands will likely be 15 to 30% greater than calculated by ohms law. It is always higher, than calculated by ohms law because of the fact that there is a phase angle between voltage and current when driving inductive loads like loudspeakers.
So yes, an amp comfortable with three ohm loads, and able to deliver power to a three ohm load is required.
The drop in impedance allows them to get that excellent bass performance from those three small bass drivers. F3 is 35 Hz, which is excellent bass performance. However you have to pay the piper.
Unfortunately those sonic ice amps will be quite unsuitable for driving those speakers. With class D switching amps, using the Sanyo chip set, distortion rises rapidly driving low impedance loads. That is why they only give an 8 ohm specification.
Unfortunately loudspeaker manufacturers, even good ones like B & W, go out of their way to mislead with specs. A term such as nominal impedance, means absolutely nothing. The minimal impedance is much more useful, especially if more than one bass driver is used. If the minimal impedance is quoted, and there is more than one bass driver, then you can go to the bank that the minimal impedance is going to be the impedance below the frequency where all the bass drivers are combined. Your 803 Ds are actually going to behave much more like a 3 ohm speakers than an 8 ohm ones.
One other rule of thumb. Whatever the manufacturer says the nominal impedance is, if it has two bass drivers, it is a four ohm speaker effectively, and if it has more than two bass drivers, it will be less than four ohms.
