Hmmm... Decisions decisions.
My speakers are SAMSON Resolv A8.
I thought maybe the Behringer would allow me to change to passive speakers some time, but never mind that.
I think I'l go with the cleaner solution of a plate amp.
80 hz seems to be a popular choice for a high pass filter on bookshelf speaker systems, so maybe I could use these instead and add them to each cable that goes from the sub to the speaker?
http://www.parts-express.com/parts-express-80-hz-high-pass-4-ohm-crossover--266-456
Or I could buy a miniDSP and get the benefit of all of its nice features. Or a used receiver. No idea, really. :\
Edit: those passive filters I linked to won't work, apparently, because they're 4 ohm and line level outputs have less impedance.
So maybe I'll get the miniDSP. I'm still trying to figure out if it can do what I want it to do. I found a seller on eBay that ships it for free Worldwide, which is nice for a change.
To keep the overall costs low, I'll borrow a jigsaw from someone and I'll try to make most of the panels of the enclosure, except for the two front baffles.