I play in a post/metal band (drop B). I use a old marshall jcm800 1960B with 2xG12T75 and 2xVintage 30, i will replace the V30 what is the best mix with my G12T75 for modern rock ?
For the extreme drop-tunings you mention we usually like the HM75's ... and you already have 2 of the Celestion equivalents ... so, yes, the ET65's should help smooth out those overly aggressive upper mids!