I don't know what the conversion is between metres of head and bar, and
therefore whether 0.5 to 0.75 bar increase is significant.

1m is almost exactly equal to 0.1 bar.

Most single impellor pumps add between 1 and 2 bar, but are far noisier. I
suspect this pump will meet your requirements. It will be a little puny for
a shower, but a massive improvement. Upstairs, you'd go from 0.1 bar to 0.85
bar, which most will find perfectly acceptable, but not impressively so.

Christian.