Brightening up caps...but wo/ pixelation

This is not about *just* brightening up screen caps, as so many people ask about, but a lot of times what will happen is that with however many methods I'll use to brighten up a really really dark screen cap to make an icon w/, by the time I've cropped it and done all that extra prepping, it looks really pixelated...but yet not sharp enough. So then when I sharpen it, it gets even worse. Any specific tips? Like ways to avoid this or even correct it?

Here's a few methods I may use:
Duplicate base to screen once or twice, and up the saturation, plus add curve layers
Auto levels + extra prepping, such as curves
Brightness/contrast (rarely)
Upping the curves right off the bat
Merely base duplications (several screen layers and an overlay layer)

Any other recommendations that could help to *not* get the pixelated effect?
Thanks in advance ♥