10 mbs 100 mbs autodetection

I have a 10 mbs network with a 10/100mbs network card at the server. My 10 mbs hub just died.
I intend to purchase a 10/100 mbs hub, and want to upgrade my PCs to 10/100 mbs nics in stages.
Will my hub be pulled down to 10mbs if I have 10 mbs and 100 mbs nic clients connecting to it? Is it only some models that this might happen to?
If so, is the best option to buy another 10 mbs hub and put a 10 mbs nic in the server so that I have a hub for the 10mbs PCs and a 10/100 mbs hub (or switch) for the 10/100 PCs.