After running out of funds I picked up a couple of Sony 12" subs for $50 each on Craigslist to pair with my Maggie 3.7i . I set the subs at about 50 hz and keep their volume low as not to get any boominess and run the 3 7i full range they integrate real well together . Audiophile friends and musicians that stop in are amazed at the great sound. By playing around you can achieve good sound at a reasonable price.
My friend picked up a free Mirage sub from a neighbor and integrated it with his LRS using the same technique just setting the sub to about 80 hz and it too sounds good.
Good luck