I can second the REL Storm recommendation from Kinsekd. I use a REL Storm III and have been very pleased with the results. By the way, I run the MG 1.6 QR in full range and use the REL Storm III to augment from about 35hz and below. One great thing about the REL Storm III is that you can choose to run your main speakers in full range or restrict the low frequencies to the main speakers and ask the REL Storm III to handle all low frequencies.
Good luck.
Good luck.