This all depends on the firmware you're running (and I don't even mean SARA vs Passport vs OpenCable)...

My local cable company runs SARA and has the "Power and Numeric" option, but they also have it set to tune the next available channel whenever an invalid one is entered. So enter channel "0" which doesn't exist, and get channel "1". They also have power saving enabled on the hard drives, which means you cannot come up with a single startup macro that doesn't end up changing channels, since the delay for the hard drive to spin up is greater than the command timeout when the hard drive is already on, so a [0], [Delay], [Exit] macro for power on doesn't work quite right either.

And of course you can't even leave them on. The cable company has several automatic power-down events each night... 1:15 AM and another after about 4 more hours. If they don't power down, the program guide doesn't update.

Best solution: voltage sensing. Serously, it's like a breath of fresh air for anyone who has tried to live with flaky automation of SA boxes.