Those Gold Lion KT-88's are magnificent. I ran them in a Cayin A88T with wonderful success. Incredible midrange.

If you ever want to try something with a little different "more neutral" flavor I can't recommend the Tung-Sol 6550's highly enough. They are quite nice indeed and can be had for around $150/quad. The Tung-Sol 12AX7's beat any other tube I tried - very nice and affordable.