If you can get the Swordsage switch, Master of Nine should be a pretty natural move. If not, consider taking one more level of Monk (yes, yes, I know, but at Monk 4 his BAB and saves increment, his unarmed damage progression moves up a step, and he gets an initiator level for having an even-numbered level in non-ToB class[es]. If you're gonna have Monk 3, you may as well go to 4.) From there, Crusader pretty much is your prestige class; you'll do fine taking it for however many levels the game runs.