I guess it's been quite some time since I've had to enter the memory size as it's always correctly detected my equipment. RedHat found my nVidia Geforce2 w/32MB (and it shows 32MB, not Kilobyte). In fact in my /etc/X11/XF86Config it doesn't list the amount of memory at all, the drivers correctly detect it.
But I'm sure it was in Kilobyte if you say it is, it's been a long time since I used XFree v3.x where the memory was probably required. At any rate, 16,384KB is the same as 16MB, you're shorting yourself if you only specify 16,000KB (not that you'll probably use that extra 384KB anyhoo. You could run 32 bit color at 1600x1400 and only use half that amount. Of course GL video games might want more than that.