I would think the Placette Active linestage would be an excellent match.
I had a Belles 150A Hot Rod for awhile, and found that it was a great match with tubed pre-amps. I tried the Rogue 66, the CJ PV10, and the Quicksilver Line Stage Remote (the 6DJ8 version). All of them mated well with the amp, with different strengths and weaknesses. The CJ was lush and rich, but had a slightly muddy low end, and was generally a little "dull" sounding. The Rogue was the opposite--very precise, detailed, with excellent imaging and control. It was a little sterile as tubed equipment goes, however. I settled on the Quicksilver, which I found to be right between the CJ and the Rogue. Slightly warmer than the Rogue, but retaining much of the detail and precision. You would do well with any of the three, depending on your tastes. Good luck!