I don't necessarily disagree with the choice of Cat 5e but these days it's not really any cheaper than Cat 6 and the latter is more likely to be compatible with 10G (which is already being seen on consumer motherboards). You can get 305m of solid core Cat 6 for £60, for example.As above cable and solid copper core 5e is what i'd go with, avoid CCA as it's crap. Going back to powerline if you're on the same circuit breaker for the sockets then it's unusual you'd get such poor sync. Have you followed the usual stuff like not plugging into an extension/surge protected outlet?