Maybe a power cleaner connected before the router/server would help? It's tough to say, and could be a wasted investment. I'd recommend you run gigabit cat 6 through the house. Do a nice job with multiple connections to every room, and you won't regret it.
If you only want to accomplish this single task with your setp, you could just run a really long crossover cable and plug directly into your box on a 2nd NIC.
Or, you could go wireless? The 360 wireless adapter is expensive, so I bought a 4-port wireless-to-ethernet bridge that connects my entertainment center (xbox360, xbox, ps2, tivo) to the downstairs wireless network when I'm using alot of bandwidth on the upstairs network (which I normally connect to with cat5).
If distance is an issue, you can use a hacked firmware to boost your signal. I have two separate wireless networks in my house, one broadcasting from the 3rd floor and one from the 1st floor. You can get nearly full-strength signal anywhere in the house, on either network.