Both your NIC and Router have different colored indicators showing the established connection speed. This is done automatically. 50 feet is nothing.
It's ONLY useful if your connecting to another PC or PCs with a Gigabit Ethernet for file transfers, and any of the speeds supporter by either your NIC or Router won't hinder or improve your Internet connection.
If I understood correctly; connection speed limits:
ASUS P5B-E = 10/100/1000
D-Link DIR-655 = 10/100/1000
RAID Box = 10/100/??
It will all be as fast as the slowest connection which is 100/?? Mb/s. Also, there are a few different ways to wire the Ethernet Cables, I assume that the cables complies with the appropriate 802.3__ used by the router. Also, while CAT 5e can work, CAT 6 is preferred and has been standard for sometime with Gigabit cabling.
I looked behind the plate in the wall and the cable in there is CAT 5 !
I need to change that...
I'm using TIA/EIA 568A CAT 5 cabling and I have no issues running my gigabit network. The reason why your system doesn't detect the router at 1G is caused by something else like ports being configured for 100Mbps. If the cables were low quality, you'd get errors and you would have to set the speed to 100Mbps; otherwise it would still try to connect at 1G. Does your PC connect at 1G if you use a short cable to connect to the router? If not, then you need to figure out why.
The problem is that the OP hasn't yet determined if there's a cabling issue. That should be the first step (at least for me). If he determines that cabling has to be redone, then I agree that CAT 6 should be used.