What matters for perception is angular resolution, not DPI. And 27" display covers more visual field that 17" from 90s, so you can and should sit further away from it. Once angle of perceived pixel is smaller than angular resolution of your eye, reducing pixel size only adds to the resolutions of shades you can show to the user in that area (closer to bpp increase, than dpi increase, because you can't see pixels anymore, but still can perceive irregularities of brightness on edges).
What matters for perception is angular resolution, not DPI. And 27" display covers more visual field that 17" from 90s, so you can and should sit further away from it. Once angle of perceived pixel is smaller than angular resolution of your eye, reducing pixel size only adds to the resolutions of shades you can show to the user in that area (closer to bpp increase, than dpi increase, because you can't see pixels anymore, but still can perceive irregularities of brightness on edges).