I have an internet connection with a cable modem. I would like to ask what is prefered way for connecting my home bussiness to Internet:
1/ cable modem + router + ASA 5505
2/ connect ASA 5505 directly to cable modem
My question is if the 1/ is considered more secure. Or am I too paranoid and 2/ would be just as fine?
Option 2 is ok in your case.
Most cable modem based ISP's use DHCP to acquire the public IP address for your edge device (ASA). Just configure the outside interface on the ASA box for DHCP.
Something like this....
ip address dhcp setroute
ip address 192.168.1.1 255.255.255.0
Hope this helps.