The Dayton SUB1200 or 1500 are within budget and can be adjusted to be quite effective and tolerable to enhance your low bass output. Set the low pass crossover frequency at its lowest setting, and keep the gain down so it's barely noticeable except for passages that contain deep bass. Experiment with placement and phase to suit.
Subwoofer suggestions for budget system?
My current setup is a pair of Magnepan 1.6 speakers, a pair of Schiit Vidars, Schiit Sol turntable w/Goldring E3 cartridge (I have a VAS-rebuilt Denon DL-103 with Ebony shell and microridge stylus when I can get someone to come set it up for me), Mani 2 phono stage, Asgard 3 headphone amp acting as preamp, Schiit SYS as source selector, Modi 3+ connected to Volumio for streaming digital and an Orchard Audio RCA-to-XLR converter to drive the Vidars in monoblock mode.
I'd like to add a subwoofer to the mix that can keep bass out of the Maggies. I'd, of course, prefer a dipole sub to go with the dipole speakers, but not terribly picky ATM. My budget is around $200 to $300 for now. I have been very tempted to build a pair of my own subs, but that's not in my budget right now.
Suggestions?