So, I've had my Bugera 333xl for about a year and a half now, and the Preamp tubes went mircophonic.

So I was thinking it's time for new tubes all round.

I already decided on 6L6's. But I don't know anything about brands and stuff :/
Also, what kind of preamp tubes should I get?

I'm going for a way heavy metalcore/deathcore sound. Like from Parkway Drive and As I Lay Dying, to Job for a Cowboy and Whitechapel.

Any advice is much appreciated, thanks guys