using the figures you've given me,
an 8.5 wheel with et -12 and a 25mm spacer to start with (et-37),
and swapping to
a 9.5 et -19 wheel WITH the 25mm spacer (et-44) will leave you with
6mm LESS space between the wheel and the suspension,
and will bring the outer edge OUT 20mm
without the spacer you'll be worse off in every way.
put the original wheel on with the spacer, then use a ruler and guage how much space you have to play with on either side.