If you were to market a product, what would you do?

Beta testers as @jond suggests, is certainly one avenue, though this is more common with items that are easier to ship, and less susceptible to damage from shipping, like cables.
For larger items, perhaps asking if you could host at some audio clubs could also provide some feedback, or stimulate sales.

Peter, you might try giving Bob Backert of Backert Labs a call, as I'm sure that he would have more developed ideas. He has launched his own brand after many years of providing repairs and upgrade service for many big brand name electronic gear.

Good luck,
John

How about designing a website?

Yes, I know that will cost money too, but if folks had a link to click on that would show them photos, features, prices, and specifications, I think that would be money well spent.