Their is many, many I have tried. I like the Shuguang...but I have found better. The Sylvania CHS-6SN7W (VT-231) is a gold metal based god-send. My favorite to this point!
You need a couple hundred hrs. on the Shuguang before it can reveal it's true light. The best, most balanced and fully fleshed tonality is offered by the Sylvania however...and a bonus is the better, more uniform control of the bottom bump that the Grado is endowed with.
Another wonderful match with the PS1K is the Mullard ECC32...very expensive however. The Tung-Sol "Black-Glass" VT-231 works well with the top Grado...just not my favorite. I like the 6H8C (Russian) with the HP-2....it's strong foundation really rounds out that phones performance. The Shuguang needs time..it is a nice offering.....and is much cheaper compared to the other elite offerings.
Thanks for your response. The Mullard ECC32s are too well known and pretty much un-obtainium now. I'll be scouring the Internet and eBay for any good deals and probably buy one tube a month for the next year. I guess the pay to play is part of the fun. At least I won't need to buy two.