generally nvidia's recent products have good linux support,
maybe you can check their website to find a suitable card. Also the kernel version used (instead of the distro number, such as redhat 6.2) will be more important if you want to check the compatibility.
BTW, if you want to use 64bits system, i think nvidia Quadro FX 1000 is good choice, but that will exceeding your budget .. :)
BTW, if you want to use 64bits system, i think nvidia Quadro FX 1000 is good choice, but that will exceeding your budget .. :)