What's your best 5U4GB rectifier tube and why?

I recently acquired a 9 watt Class A design 300B tube integrated that came with a 40's NOS Japan 5u4gb rectifier that I wanted to compare to some of the best that's available. I'm new to tubes so I'm asking for your expertise.

It would be helpful to know why you're high on your particular tube recommendations and what differences one could anticipate with those you're suggesting to sample. Acquisition cost for same would be very helpful as well.

My amp is currently running with a pair of Shuguang Black Treasure 300B's and a pair of Black Treasures 6CA7's, in conjunction with a pair of Psvane 12AX7's all combined with the 'rec mentioned above.

Thanks in advance to all for the assist!