Failover internet connections, and implementation...

I've a question about failover internet connections. I'm interesting in
knowing what kind of implementations that other SMB's use for redundancy,
and to switch to in the case of a DOS attack. 

Do any of you have redundant highspeed internet connections for your offices
(versus those for datacenters)? If so, what kind of setup do you have?

Here's the setups I'm considering...

1. Have a second cable modem/dsl modem active, but not hooked into the
network. In the event of a failure, move the connection for perimeter
devices over to the standby connection and reconfigure the perimeter device
to use a different IP.

2. Have a second set of perimeter devices (firewalls) programmed to use the
IP's on the second connection, as a hot standby.

My problem with the first option is the time it would take to reconfigure
firewalls and IDS' to use the other ISP's connection. The problem I have
with the second is the expense of firewalls and IDS' just sitting there
idle. 

Any input is greatly appreciated!


Dan