300tdi 5 door sills

Hi again

MOT time early in the new year and prob gunna need welding or new sills on my `94 300tdi 5 door, but was just wondering what best and/or strongest mod i can do to these, heard a lot of stuff about box section steel, if there is owt better than just standard sills, i would consider it, and maybe some rocksliders at the same time.
Any advice is appreciated

thanks
Craig

SEARCH !!!!!! Been covered about a zillion times mate