Why do you need two connections?
Do they both need to be fast? Would wireless speeds be ok for one of the connections?
(I'm not saying that you don't need both, just curious on your setup

)
In short, its a home server that serves computers in the house with various HD media, also my main rig backs up to the same server via genie timeline, daily it backs up many GB's of pics as well as HD video, also I have around 8 wired I.P. security cams. When the IP cameras are on it grinds to a halt for some reason, the router is a sky one (RUBBISH) and cant seem to handle the data, iv seperated it as much as possible, it hangs off a gigabit switch, but sky see it fit that only the sky router can be the dhcp server (have asus n56 wireless router - tried forever to get it to be the dhcp, but the sky isnt compatable)
The problem is I need all internal computers to access the net and the server.
So ill make an entirely seperate network for the ip cameras....why I need another adaptor and as its loads of video data it really needs to be wired.
So the main network will be basically 2x gigabit switches where computers can access the server to read/write to it.
Then I will access the internet only via wireless connection
and 3rd connection will be IP cameras.
All this because sky cannot be bothered to build a proper router.
This way only 4 computers + ipad + iphone will access the sky router wirelessly and it will be blissfully unaware of all the other data on the network.
Sorry long post, hope it makes sense.