Sven, Hughes & Klinsmann, of these 3 I would rule out Sven right away!
Leaving Hughes & Klinsmann, Hughes did a really good job on a budget at Blackburn (similar club to Fulham), then got a bit carried away at Man City buying some over inflated priced players. However Mancini is doing the same so market forces actually make Hughes' signings better all the time.
Klinsmann was behind Germany's WC semi in 2006, managed for 1 season at Bayern I believe, then out of the game for 3 years.
Hughes looks fav, but I can't help thinking Fulham will go for Klinsmann.