Would you consider this lowering?
I would get the adjustable one because I like the uh... adjustability lol. Seriously though it really helps if you go with wide tires and wheels. My car had the hose mod done when I got it and I put it back stock so the rearend had more suspension travel before hitting the exhaust system and I had to re-adjust the panhard bar after.
if your gonna spend the money to replace the bar get an adjustable one regardless, doesn't make sense to spend the money on the fixed one to me. it's like buying a dvd player when a blu-ray player costs 10 bucks more.
Do you "need" an adj phb? Probably not, but like everyone else is saying, don't waste money on a non-adjustable, especially if you plan to go lower in the future. Could use this as an opportunity to get a watt's link 
