Schwalbe marathon plus can be found at 47$ at ebay. Don't know if it's really worth it compared to a 2 times cheaper tire as you haven't used your seca at the rear from start. The thing is that you can buy the same 20$ tire and use the old one as a puncture-proof liner by cutting the side of the old tire, gatorskin or seca by the way. I'm on Schwalbe now i would have done that if my old tire wasn't a studded tire.