help need with cybercafe network configuration

10 computers will easily run on one server.
Most basic setup would be:
Internet -> modem -> server -> switch -> computers
Switch would be either a 16 or 24 port switch. depending on what you can afford.
Might also look into getting some wireless access points for the laptops.

You should be able to run both lines into one server. Use load balancing software to equalize the load on both internet lines.

Now if you want to do away with the server completly you could just get a router for each internet line and then an 8 port switch.
The routers would handle your DHCP for you.

What were you planning on using the server for?