01 Tacoma rear sag

i have an 01 Tacoma and i do a lot of camping and put a lot of weight in the back of the truck and on the top of my shell. when i am fully loaded up my rear end sags quite a bit. i am looking for something pretty cheap to solve the probably something like airbags. what im wondering is if i should do a lift or add another leaf spring or airbags or something else??? Thanks!

 

New (stronger) Leafs from General Spring; $130 - $180 a side: http://www.generalspringkc.com/Leaf_Springs_Toyota_Tacoma_2001_2002_2003_2004_s/1932.htm

Progressive AAL from from Wheelers; $150 - $160 for the set
Regular: Heavy:
These are the options I'm considering