I have to chime in here.
Yes a downpipe is worth it.
However it is worth it when your putting an entire exhaust on. If you already have an exhaust on but stilll on stock dp, it may not be worth the money for the dp and the labor to get the 9hp.
If you were going from stock exhaust to a full TBE then its worth it.

If you plan on going BT (bigger turbo) later that is when I would install it. If you do not plan on pushing much more power then I would say forget about it/sell it.

If you already have it I would install it, and it looks like you are going to take it to a shop so if they do it for ~$100-150 then why not, pay that to get yourself an extra 9hp


my $0.02