Canary M-500 Monos- which 300B tube-

Bopper,
Keep in mind that EML makes a standard 300b, a mesh plate 300b and the XLS version 300b. I haven't heard the standard 300b but I understand that it is very good. I can personally vouch for the Mesh and XLS versions. The EML aren't inexpensive but their performance justifies the higher cost. The standard EML 300b could possibly be the best value of their choices when multiple pairs are needed as in your case.
Charles,

I have a pair of the M500's. They are my favorite amps that I've ever had. What works really well with them are the Sophia carbon plate 300Bs. I also used a full set of EML 300B XLS which are also very good tubes but the Sophias have more lively sound and I like them better. Both of these choices are already around 600 a pair and you will need 4 pairs, so consider the cost. I think the tubes should last a good amount of time however because the bias is relatively conservative on the Canarys. I also had a VAC Renaissance 30/30 where I was trying these same tubes and it liked the EML better, although the VAC is harder on your 300B tubes.

Most likely the Royal Princess and the Takatsuki are probably going to be too costly to be worth it.

Cfchew makes a good point, the preference for a given tube will vary with a particular amplifier. My Frankenstein SET sounds better with the EML compared to the non Royal Princess Sophia tubes, no comparison. This apparently is not the case with the Canary(different topology, circuit etc.).
Charles,

I have the M500s since 2010 with the Sophia 300b Mesh. Excellent sound and no bias issue. If you are having bias issues, you should check if your voltage is fluctuating, particularly while trying to bias set.