Re: second hdd possible at fit-pc2i?
It's not the cable that allowed to use two IDE devices on one port, it's the IDE interface itself that was designed for up to two devices. With SATA this is not the case.
The "special adapter" you probably have in mind is called SATA port multiplier. It is not very cheap, not very small and not very easy to find (for example: http://www.addonics.com/products/ad5sarpm-e.php
In the case of fit-PC2(i) it is also not very useful, because the hard disk controller in fit-PC2(i) is IDE with IDE-to-SATA bridge attached to it, so the speed of the internal IDE interface will be the bottleneck. If you connect 2 hard drives to it, the performance with both drives used simultaneously will be comparable to USB 2.0.
Most importantly, a port multiplier will likely not work with fit-PC2(i) at all, as it requires special support on the SATA controller side (which is a IDE-to-SATA bridge in this case, so I can't imagine how it could possibly work).