I'd say you defiently need SP.
Unfortuently it doesn't look like you have alot to play with on offense to try and acquire SP. You've got a pretty solid offense, but not alot of depth. You could wait till the first month or so of the season is over, and then deal either anderson or sosa, and insert berkman into your lineup, and just go with the starters you have until then, thats probably your best course of action
If you feel you can't wait that long, I'd probably look to deal konerko for a solid SP, but I think konerko is gonna come back down to earth this year, so it depends what kind of numbers you feel he's going to put up.