You would be better off buying the USB 2.0 PCI card.
If your PC only has USB 1.1 capabilities then plugging in USB 2.0 equipment (including external hubs) will work but only at USB 1.1 speeds (c. 12 Mbps). If you want the higher speed of USB 2.0 (c. 480 Mbps) then you will need to install a USB 2.0 PCI card in your PC anyway as I have already pointed out. Then if you plug in USB 2.0 equipment (including external hubs) then you will also benefit from the faster speeds.
The EverythingUSB FAQ that I posted earlier will probably answer most questions that you have about USB 1.1/2.0.
The USB 2.0 PCI card will give you a few (usually up to four) USB 2.0 ports. Only if you need more than that do you need an external hub. If you are connecting a small number of USB 2.0 devices (note that the devices must also be USB 2.0 in order to benefit from the faster speed otherwise they will still only work at USB 1.1 speeds) then you don't really need an external hub - if you do find that you need one later on then you can buy one then. Does that make sense? Perhaps if you post specific details (makes and models) of all of the USB 2.0 devices that you'll be using people can comment?
Most likely you will only need USB 2.0 for large data transfers between the camera and PC. The other devices may well work just as well with USB 1.1. But check the specs. If this is the case then you can continue to plug all devices bar the camera into your existing USB 1.1 ports on your PC and just plug those with high speed data transfer needs (e.g. the camera) into the USB 2.0 ports once you have upgraded your PC with the USB 2.0 PCI card. Make sense?