MC275 with mixed tube rolling

I'm planning to have tube rolling for my MC275 V5 (2 of them in monoblocks).

I'm thinking of -

1. Genalex - Gold Lion KT88 Power Vacuum Tube reissue.
2. Tung-Sol ECC803s 12AX7 Gold Pin Preamp Vacuum Tube
3. Mullard 12AT7

My Qs is whether having these 3 type of tubes from 3 different makes/brands is a good idea ? Or should I have all these tubes from a single make/brand ?

This is a very interesting question. However, there is not a single person on this forum or any place else who can answer it, especially the guys selling tubes. It depends on your system, which also includes your room and your personal taste. That is what tube rolling is all about. If you do this right you should end up with a nice collection of tubes you will never use again. The rising cost of tubes is a good reason to give solid state some serious thought.
The rising popularity of tubes is actually causing them to get LESS expensive, except for the NOS and some older stuff which, although possessing mystical properties justifying the silly high prices, don't always seem to be the better option. I bought 4 matched Sovtek KT88s for about 100 bucks, and a matched quad of Tung Sol KT120s for under $175. Hardly expensive. Also, the tubes you mentioned are made at the New Sensor factory so they're all sort of the same brand. Regarding your personal tone preferences, talk to thetubestore or upscale audio or somebody and they can suggest a 12ax7 you might not have considered, and many are guaranteed and returnable if they don't do it for you. I like a more modern and even tube tone so I stuck a Chinese 7025 pair in my amp replacing some otherwise nice 12ax7s and they do exactly as they said they would, making me satisfied and slightly taller.