Sunbeams are still my faves, the round core and smooth feel are just bliss. But they are low tension, and coming from high tension flats there will be a huge difference for you.
So since price is the main factor in your decision, I'm going to suggest Rotosound RotoBass strings. They have become my favorite low cost string and will use them before even considering D'Addario. I think they are basically Nickel SwingBass without the silks, so they are cheaper. These actually replaced Sunbeams on my Warwick, they are tighter and snappier which is what that bass needed. They are not nearly as smooth feeling though, but that's Rotosound for you
Rotosound Rotobass - 4 String Set
Jason will get you an even better price on them once you register on his site and tell him you're a TB member.