Mixing tube brands

depends on your amp and how bias is controlled.  My amp has great bias control and I should be able to adjust the amp to use them in symmetrical pairs so long as they aren't far apart, and IIRC, I've used both of those tubes and they were similar.

I am a bit OCD and always try to have the same brand tube in the power bank, then in the pre amp the same brand across the bank/type.   

The only real concern is IF the manufacturer calls for matched pairs being used.

Brand mixing? Maybe if it is an American N.O.S. mixed with a Russian-likely power struggle resulting in blown expensive, aftermarket fuse.

Russians & Chinese are in cahoots so no problem.

"blend the sound" What the heck is that? 

My amp easy to bias with the controls right on the top. All the tubes are KT88's. If I am to try it. Should I do one side as in tube number #2 and #4 with the Gold Lions and #1 and #3 with the Psvane tubes? My amp has the 4 small tubes in the center and two power tubes on each side.

Kevin may not like it that my amp is Chinese and very similar to the Prima Luna. Although I did buy the 12AU7 tubes from him.