Gigabit LAN Connection

First, let me start by saying how thrilled I have been with my LimeTech unRaid Pro setup for over 3 years!  It has been one of the most reliable and consistent pieces of tech in my quite formidable home tech collection.  My configuration is identical to the early Lime Tech pre-built packages using the ASUS P5B-VM DO motherboard and currently has a total of 15 drives 6x WD EARS 2TB drives and 9x WD EADS 1TB drives running the latest stable release of unRaid 4.5.6.  Everything works great and I have found the ease of which I can upgrade drives over the years to be simply outstanding. A couple of years ago I began upgrading my entire home network (32 devices) to Gigabit which has gone about as smoothly as things tend to go. 

I have never been able to get the P5B-VM DO on the unRaid box to do Gigabit.  I have used 10 different CAT6 cables from different makers and through the years have upgraded and changed out my switches so I don't believe it is a switch problem.  It hasn't really prevented me from get tremendous value from the unRaid box, but it is now the only device in my entire network that is not Gigabit and that one amber light on my switch is kind of bugging me.

I spent the last few days searching and searching the forums to see if anyone else had experienced the problems with my specific motherboard and most problems reported seemed to have just vanished either through re-seating a cable or fixed through upgraded release of unRAID.  I am not sure if am alone out here on this older motherboard but as it has worked so reliably for so many years I don't see a reason to junk it.

ethtool does show that the box is capable of 1000 and that is advertising with autoneg on.  If I override the setting using ethtool and force it to 1000 full duplex and leave autoneg on then the light on the switch blinks green for a second, goes out and about 3 seconds later I hear a beep from unRAID and it reverts back to 100.  If I force it to 1000 and turn off autoneg the light on the switch goes green and stays green, but I can't talk to the box via the network.  Using the ethtool after this shows speed as ?? <unknown>.  In addition, I did upgrade my motherboard BIOS to the latest as well last night just to see if it would make a difference, alas it did not.

So having said all of this here are my questions for this august group:

1.  Does anybody have a P5B-VM DO motherboard running the latest release of unRAID operating at Gigabit speed? If so, what type of CAT5e/6/7 cable are you using Patch, etc.

2.  If I have to abandon the LAN Adapter on the motherboard what card does anybody recommend?

3.  Any 'tricks' or configuration 'tweaks' that may be worth investigating to solve this problem?

Any and all help is both warmly and greatly appreciated!