I just switched over to a windows XP machine with CRT EMU,soft 15khz and powerstrip so I can use my radeon hd4890.
Being able to create accurate resolutions makes Capcom games looks noticeably better than they did with my old windows 7 pc with my arcade vga card.
I tried street fighter 2 at 384 x 224 and it looks less pixelated than the closest res on the arcade vga which was 392 x 240.
With powerstrip, I can create a resolution within a resolution which would allow me to create 224p within 240p. That should make it 100% accurate but I haven't tried it yet.
People say that when using 240p for 224 line games, mame automatically adds black borders to keep things accurate. I am going to test it at both 384 x 224 and 384 x 240 to see if they come out the same.