The combination of low (of fairly benign) impedance and low sensitivity makes Maggies one of the few cases for which I routinely suggest an external amplifier. My current system uses Emotiva amplifiers and an Emotiva processor. Previously I used a mid-range Sony AVR (was not happy), near top-line Denon AVR (did OK but much happier with external amplifiers), and a Pioneer Elite (old SC-27, this is the only AVR that seemed to do OK, but I already had the amps so barely tested the AVR alone). I have used all sorts of amps over the years from a 35 W Eico tube amp through hybrid of 75 W tube (ARC)/200 W SS (Counterpoint, tube inputs) and innumerable SS amplifiers. I love the sound of tubes, knowing full well mostly due to the distortion and microphonics they add to the sound, but quite frankly Maggies to my ears have always done best with a good SS amp. The SS amp controls the bass much better, going deeper and tighter, and struggles less dealing with the low impedance of the ribbon tweeter. If I had infinite money I'd probably get Bryston just because I like them, hey are built like tanks and Magnepan uses them, or Roger Sanders' big amps. As it is, the Emo's are doing OK for me.
Timothy, does the manual say what the correction factor should be? If they are sensing voltage as I suspect (usually easier than sensing current) then halving the resistance (speaker load) means twice the power for the same voltage. IF the amplifier is not current-limited, then the lights will work the same in that case, with the caveat that 0 dB is twice the power at 4 ohms as it is at 8 ohms. The fact they mention a correction factor implies there is such a factor somewhere so hopefully you can find it.
There are a plethora of good subs these days. That is one thing the whole HT revolution has done for us IMO. I was biased toward servo designs from when I first built my own sub ages ago. Rythmik uses a very similar scheme (guess I should have patented my design way back then
), and Brian Ding's day job is similar to mine, so we had a lot in common on several levels. I have been very happy with my Rythmiks. I went sealed partly because of bias but also because I don't have a lot of space and in a small'ish room the slower roll-off yields more impressive response.
At 8' away a pair of Maggies should deliver about 105 dB SPL driven by 350 W. That is %$#@ loud for me. See e.g. http://myhometheater.homestead.com/splcalculator.html
HTH, IME/IMO, my 0.000001 cent (microcent), YMMV, etc. - Don