What would be a good, cheap, durable head to plug into a harkte 400 watt XL series 410 bass module. Around the 250 range
I recommend anything in your price range by hartke. I have a cheap combo by them and I've always loved the sound of it. But just make sure you get something with Neutrik Speakon output (as long as your cab has the input for it). But once you have what you are willing to spend (maybe an extra $150 cause we always see that next thing better haha) get your ass on craigslist man!!!! find something, look up product reviews, and ask them if you can try it out and make sure you like it and that its working. you can find much higher end stuff for low end prices there. Gallien, markbass, Genz benz, Hartke, these are all bands you should try to find and try out. Reliable quality and common so you might find that used steal of a buy. my amp sold for 1600 new and I got it for 350, go figure.
If you are ok with looking used, you can find an excellent amp for cheap. Something like a Hartke, Ampeg, GK, Peavey, etc, depending on the sound in your head.