Well, I have the X2's and I must say that the combination is intoxicating! Such involving sound, I wouldn't have thought that a tube amp would ever pair well with the X2's but indeed they do!
I'm just a week or two in to rolling this tube that I've recently bought local through ebay...
More info on it here at upscaleaduio.com: http://www.upscaleaudio.com/philips-pcc88-7dj8/
Compared to the stock tube, I absolutely love this tube! It is an outstanding sounding tube especially for the money I paid!
The highs are sparkly and clear without any fatigue, the bass is so well textured and powerful compared to the stock tube and the mid's (oh boy!) are just captivating! Listening to albums like Eric Clapton 'Pilgrim' was a surreal experience!
I'll be looking at Matsu****a, Mullard, Seimens and Telefunckens next, but this Philips tube will do me for a very long time! Also I'm loving that I'm using a Philips tube with a Philips Headphone, ohhhh the irony!