I've thought Berba going to you would make sense for ages, but I wonder if he's the wrong style of striker. When you consider the service Bale and Lennon can provide from the wings, and indeed how intelligent VDV's passing game is (hasn't been that evident this season because of what's in front of him), a striker with good, sharp movement who's good at getting ahead of defenders would be a better alternative. Berba isn't quite that player. You get the sense Crouch can't always keep up with the speedy build up on the wings, Berba might be the same. I know Defoe fits part of that description but he has had a bad season, not the calibre of player you need even at his best anyway. Essentially you want a better version of Darren Bent.
Ideally you'd have someone who can bring VDV into the game as well, asking a lot of one player but it's what you need to make the next step. The Leandro Damiao rumours could work, I don't think he's a typical Brazilian striker, more of a physical presence and more aerial ability than you'd expect. Haven't seen too much of him though. I know Falcao is where the current hype is at but he'd be the right type of player, not sure you could get him without CL football though. Suarez could have worked. Not sure of other names really.