I just bought an fx5 from ebay. Brand new, and came with carbon + polishing pads. It was a really good price (at least compared to anything else in Canada).
The user is mickydonald12, and they have a whole bunch of them.
They start at $154.99 USD and I haven't seen them go much higher than $160.
Shipping to Canada is $54.90 ($64.90 for express).
So for me, it came to $210 USD with shipping (~$220 CAN when I bought it). Then $11 customs, for a total cost of $231.
Compare that with $350 in the petstores, + 12% tax in BC (for a total price of $392).
So I saved over $160, and it came with the extra media!
They were a bit slow on shipping (5 days after purchase) but it only took a week to get here.
Anyhow, if you're in the market for a new, big, filter, this is definiatly worth a look!