small office needs networking advice

Hi:

Our small office is moving, so it's time to reevaluate our network setup.

We're a Windows 2000 office with 8 full time employees one Windows 2000 server, and one Linux Server, and a couple of development machines.  We also have about 5 other workstations that are used part-time.  

We use a DSL modem to connect to the internet, a cisco router and then two Linksys switches - one 16 port and one 8 port.

As for usage, we're a writing school not a film editing studio, so for the most part we don't move large amounts of data over the network.  The bulk of the traffic is running MS Access queries to our Access database.

My questions are as follows:

Is that one uplink between the 8 port and 16 port switch a possible bottleneck?  Will we get a noticeable difference in performance from using one 24 port switch rather than one 8 and one 16?

Is there any real advantage to upgrading our switches?  We had a problem a couple of summers ago where a switch was failing and it corrupted our Access database repeatedly before we realized what was happening.  We've replaced the switch, but it makes me leery about using Linksys products again, but Cisco's 24-port switches start at $555 and our budget is small.

Did we just get a bad switch that one time, or is it generally a dumb idea to use Linksys switches in a small office setting?

What is the advantage of using a managed switch over an unmanaged switch?

Last question - if we have a lot of ports on the switch that have wires plugged in but are left unused (without computers plugged in) will that slow down the network?

There are a lot of questions here so I made this a 500 point question.  I'll spread the points around to whoever helps.

Thanks,

-Charlie