In reply to Professor Bunsen:
If you're going to get a filter I'd just go for the Hoya 'HD' ones. They're not too bad price wise if you look online, and they pretty much the best of the market for actual photography (as opposed to spectrum analysis).
€125 for a 400x seems crazy. I didn't paid that for a Lexar 16GB 1000x!
I'd go online and get a 1000x card, very useful for cameras like the 5D3 that produce a lot of data.