Transparent Reference XL is a perfect match. I have an extra pair if you need any.
Before you go off to spend lots of money, $1000s plus, try out the SilverAudio cables. Great great resolution and a perfect match with tube gear. I use ARC tube preamp and amp with Magnepan speakers. Check out www.silveraudio.com for free home trials. I have compared Transparent, Straightwire and Magnan and found the SilverAudio to be an excellent product. Just too much of this can make a system sound too analytical just like too much of Transparent can be too warm and loss of resolution. My own experience is that interconnect cables make a far far greater difference than speaker cables. But then again, I try to use as small a speaker cable length as possible.