When you boot Haiku, try to enter boot menu. Here you can select the vesa mode. With a bit of luck, you will find here what you’re looking for.
Otherwise, in /system/var/log there’s a syslog file where you can find some infos. For example, you will find what are EDID infos given by your monitor and so supported modes. If you scroll up from this point you will find infos reported by the VESA BIOS of your graphic card also with a list of supported mode.
Then, if your graphic card and monitor are supporting it, it is possible to add an additional mode in vesa file located in /home/config/settings/kernel/drivers.
Aside of that, a lot of “old” Nvidia cards are supported, it’s surprising.
Could you provide more infos about the card? You can use listdev command for example.