Aronsss,
I've had my LL2 deluxe for about two years now, and use it with a DIY cable by Chris VenHaus (VHAudio), and I'm very happy. I cannot comment on the best cable, as I have not tried others (other than stock, that is).
You might want to dig my threads, as I asked about power cables. Some answers came back saying it didn't matter much because of the power treatment inside the LL2, others talked about very expensive cables such as top of the line Purist Audio. Purist Audio was mentioned quite a bit, and in general with Lamm stuff, but I only use their ICs and speaker cables. Can't comment on their PCs, but they are expensive.
BTW, I recently replaced the stock fuse with a Synergistic Research with good results. It is not like upgrading the component altogether, but a nice improvement for the money.
I did upgrade the stock tubes, triggered by one tube that started to make noises. Didn't get the super tubes yet as I was feeling other upgrades in the signal path needed to happen first, but again nice improvement.
I love the LL2. Mine drives a McIntosh MC275 and B&W 804S. What are you driving with yours?
