just for clarification - you cannot acces SPARE S160 Ironport?
Even if you have modified the default configuration and you cannot access the GUI, you should by able to access the appliance via serial console in any case. Using the serial settings as described should enable you to see the start/boot messages after powering up the appliance. At least, you should be presented with a login screen.
If not, verify your settings by connecting to the new S170 appliance. If it does not work, your setting/serial cable/serial port on laptop is damaged. If it works, so the spare c160 is damaged/faulty, too.
Another point is, if you get the login screen on the C160, but you can not login (password forgotten), bear in mind there is no password recovery implemented on Ironport appliances. You have to open a TOC and provide the Support Engineer with serial number of C160 appliance.