You know, i saw a set of 4 pipes just like that on a PT cruiser, and i just thought it didn't look right.
The 4 may look good on something like a Corvette which is wide, but on a smaller car, it just may be too much, especially if they are together. I would like to see what 2 pairs (2 on each side) would look like if you are going for the look of 4.
Just my opinion.