Switch + Hub = Slow LAN?

[ztein]

Hello.

I have a network of 20 computers, plus one server.

20 computers divided into 2 tables therefore resulting in 10 PCs on each table.

One table has a 16 port 10/100MB switch to which 10 PCs are connected, and the second table has another 10 PCs, but they are connected to a 16 port 10/100MB HUB(not a switch).

Hence switch and hub are connected together, and the switch also is connected to the server(since its closer to the server).

Will having switch and hub working together result in increased latency?
Would it be much better if I replaced the hub with identical switch?
Is it better if I connect two switches through Uplink port? Will it increase LAN's performance? What cable is used(straight-through or crossover)?

Thanks.