ARC D-115: What tubes and cables?

I always used 6550 tubes from ARC with this amp.
In your header you also ask about cables.
I found Purist Audio to work extremely well

Goldeneraguy, I was using Radio Shack 18ga solid core cabling with the D-120. (No kidding). So Purist seems like a gigantic leap. Any other sugestions?

I'm using SED 6550's which are a great tube in my D70Mk2. Also using a pair of Nordost Red Dawn 2's...very quick and open/transparent cable. If you can source a set of GE 6550's, they would also be a great match. BTW, KT120's will NOT work in the D series amps.

Wahwah ,Yes Purist wires would be a giant leap ahead.
Magnan worked well at a more reasonable cost
Without knowing your complete system its difficult to suggest what should work for you but I would upgrade the Radio Shack wires before replacing the tubes

Yes!-Sorry for not being specific on the issue- The RS wires was one of those things that simply clicked with my system, and I was really surprised by this. And NO,they do not work well with the D-115. (It is a Mk 2 Hifi Geek).
Here is my System:
Modded Sony DVP 7000
Berning TF-10
Audio Research D-115 Mk2
Proac Studio 200
Audio Magic Xcallibur interconnects/cables.

One interesting development: Last night in frustration I angled the speakers INWARDS quite a bit from the usual position and Imaging improved nicely! However, they still do not dissapear as when I was using the D-120 with the Rat Shack solid cores.