@stephenw10: Damn it! The info about "It's worth noting that there is no point in buying a card with a high transfer rate" came a little bit to late for me :D. Well, it's just ~35€ so everything is fine.
It's this one: http://www.amazon.co.uk/gp/product/B00422IVLC/ref=noref?ie=UTF8&psc=1&s=computers
I went for the 8GB CF card since I was afraid of the 4g limitations on some CF cards.
Yes, I tried out the work around of JimP and it worked perfect, but something slowed down the firewall again and I'm kind of tired to remount it every time again. I'll just switch back to 2.0.1 and wait until a stable, hopefully properly working with my CF card, 2.1 version is out :).
I was always wondering what the difference is between those 1g-4g versions, thanks for clearing this up.
Thanks for your support and all replys,
Szop