I would consider investing in a Cat7 infrastructure, even though it may be more expensive (being very future proof). With regards to the Cat socket, definitely get sockets that have shielding! Also, check out this document: 

Beotex, 

That sounds very similar to my setup. I'll have Beosound 9000, Beosystem 3 and four Beolab 3's in the room and just want to hide the cables. I could just run long Powerlink cables under the floor but wanted to make it look a bit more professional. Nice to hear you have used a mixture of B&O cables and homemade connectors. 

Stoobie 

I have the same setup en things are working smoothly. In the end I decided to go mainly for CAT6A shielded cables to assure my home network is sufficient future proof and can withstand interfering signals. One step further is CAT7, but I think that pending the distance you have to bridge, CAT6A is normally more than adequate for residential buildings.

For audio lines I also used the B&O power links. Partly ready made by B&O en partly with high quality RJ45 plugs made myself.

Please be aware that the former master link and the various types of power link (including those with RJ45 plugs)  is of good quality and suitable for audio. CAT5 cable is not created for such usage. So please do your self a favour, buy a good quality cable and RJ45 plugs.

Cat7 is definitely overkill, but you never know what the future brings so it may be worth putting in the best cable while you are at it. However, basically any cat cable (if it has shielding) is suitable!