Storm Cat, the world's most expensive stallion, figures to stay that way. His fee will remain at $500,000."We considered going up, but realistically that's the right number," said Ric Waldman of the Young family's Overbrook Farm near Lexington, where the 22-year-old stallion has stood his entire career.There were several reasons to go up. Storm Cat topped the Keeneland September yearling sale, with a $1,766,731 average. His 15 stakes winners are the most for any stallion this year, and his sons Giant's Causeway, Hennessy, and Stormy Atlantic rank first, second, and fourth, respectively, on the sires of 2-year-olds list. Storm Cat is fifth.Storm Cat (Storm Bird--Terlingua, by Secretariat) impregnated 95 of the 109 mares he covered in 2005. So how many will he cover in 2006?"We don't set a number going into the season, but we'll cut back," Waldman said. "We figure out the demand, the mares that are on the book, and how he does during the season."