I am a big believer that subs are critical to full range sound. Most rooms do not support full range passive sound and need correction below in the bass.
With that being said far more important than the sub you use is how it integrate. Some options you listed are fine just have to decide what fits your budget and look.
You really want a system that will let you cut the bass to your mains (highpass filter). If the speakers go down to 55hz they will be far less distorted (not that they are…) at 80-90hz.
A preamp with bass management is probably the simplest. The best sound/flexibility probably comes from outboard crossovers like the JL Audio CR-1. Also a miniDSP could really do the trick too and they are cheap but kind of hard to setup from what I understand.
Now for some rambling about the speed of sound….
At the very least your speakers bass will be canceled (lumpy) if you set the speaker anywhere between 39” and 7.2’ off the front wall. I choose to have my speakers far off the wall and my subs 30” off the wall and this fixes the cancelation issue to a point. The higher the crossover the closer your mains can be to the wall. With 80hz crossover your mains can be 59” with a 60hz crossover your mains need to be 78” off the wall… gets pretty crazy. You could set both under 39” but not sure how the soundstage will sound and it will be very room and speaker dependent.
“You can calculate dmin, the minimum distance from your speaker to the wall behind it, using this formula:
dmin (feet) = 1.4(1125) / 4f-3dB
or
dmin (meters) = 1.4(343) / 4f-3dB
Where f-3dB is your loudspeaker’s low cut-off frequency. For example, if your speakers have a -3 dB low cut-off at 55 Hz, dmin = 2.18 meters (7′-3″).”
http://arqen.com/acoustics-101/speaker-placement-boundary-interference/
