In my experience, interlaced modes in the 24 kHz range look really nice. So if you're not allergic to interlace, you can use 2560x768i or even 2560x800i.
Notice that the ms929 preset won't do interlaced modes in the 24 kHz range by default. You'll need to redefine it like this (both in VMMaker 2.0 and GroovyMAME):
crt_range0 15450-16050, 50-65, 3.910, 4.700, 6.850, 0.190, 0.191, 1.018, 0, 0, 192, 288, 448, 576
crt_range1 23900-24900, 50-65, 2.910, 3.000, 4.440, 0.451, 0.164, 1.048, 0, 0, 384, 400, 768, 480