But should I go for 603e or 603e+ ? what is the difference? (if both is 233)
The difference between a 603e and a 603e+ is only the SCSI-II controller. The 603e is missing the SCSI controller, and the board can't be upgraded, so if you use SCSI devices you must buy a 603e+ board.
Oh, and is it combatible with a mediator board? -As far as I can see It's plugged in the same place as my 1260Blizzard...
It's just a question of free space above the slot where you install the board. I have a RBM tower, and there are no problems inserting the board there, but then again, it's a hight tower...
If you have the Mediator and a Blizzard1260 already it shouldn't be a problem