Sure, I understand.
I'm a little worried about the "likely to be worse if you use sf::Sprite" - we load a number of 2048x2048 spritesheets and SetSubRect on them to a sprite.
This is the core of our system, given that we only do 2D stuff, so any loss of performance will make me think twice about this update. We have to work on some old hardware (like Intel Extreme Graphics on a 1.8Ghz Celeron).
Thanks