Soldato
I have learned patience so i can wait i am not fond of the 290x or 780 to be fair it is very late now in the lifecycle for £400 and £550 and then have to compete on the MM with cleaned up cards a lot older.
Im curious as to the minimums in heavy action with two though, I reckon if i can chop 30% off whatever people get i could judge maybe if it is even worth waiting. Or as you say look for a cheap 290X somewhere and hold out for 16nm.
If it helps, I just played a bit with a single 290 @1100/1250 with Mantle @ultra/4xAA/100% on Shanghai (64) and I'd say it averaged ~85-100fps with peaks of ~155 and the lowest min I saw with an exploding tank was 71.