Dealer vs outside parts vendors

[jrcui]

I just bought my first Boxster - A 2000 base model (high miles 103K) - so I'm doing whatever maintenance a Newbie can do without getting into too much trouble. The other day I bought a replacement part at the local Porsche dealer and got the part for a price cheaper than I found online. Going with the logic that the dealer's prices were good, I went back to the same dealer and got a cabin air filter (without checking the net). I paid just over $50.00 for the air filter and installed it.

Since I like to torture myself, I checked online and noticed a wide range of prices for the Mann filter - anywhere from $50 to $12.00. Since I don't want to get reamed again, who are the best vendors to get the best prices (I already know about Pelican - since I've bought parts in the past for my 914).

Thanks in advance