You'll want the gaskets for the Alpha 10 and we have them in stock. As for the coils, I expect to have them any day now but they haven't arrived yet. I don't plan to sell the coils individually, but since you've already purchased our crossovers I'd be happy to make them available to you if you'd like.About HF horn mounting, Bill Martinelli makes a stand for his wood horns but there is no such thing for the H290's. I'd suggest making a small box for them and I think that would be an attractive solution.