Ameriquest Mortgage and IndyMac Bank ranked as the top originators in subprime and Alternative A production, two segments that have defied gravity in 2005 while more traditional markets have receded. The white-hot glow of the subprime market has dimmed somewhat in 2005: new originations are up “only” 11.4 percent from the first half of last year to $274.0 billion. At the same time, the Alt A business has surged 81.0 percent in 2005, with midyear… [One data table included]