Scan at 600 dpi then.
This is the main difference between cheap and better scanners. A cheap scanner will 'interpolate' at high resolution (ie it scans one pixel and makes 4 out of it). A better one will truly scan at higher dpi.

Most modern scanners state 1200dpi or better. A $70 scanner will interpolate, a $170 one will not.

I will post some scans here to demonstrate the difference at different settings.