Sorry, I forgot this amp didn't do audio over HDMI.
There are two possible ways of making up the HDMI video connections - through the amp, or direct to the TV.
If you connect them to the amp first, you would only need one HDMI connected to the TV. This is handy if you have a limited number of HDMI inputs available on your TV, or if you just want to reduce the amount of cables connected to the TV. The downside is that you need the amp on constantly while using any of the connected devices. This may not be an issue for you, but I know some people like to revert to the built-in TV speakers (say late at night, if you have young kids or whatever).
If you require the HDMI switcher for any of those reasons connect the PS3/350 through the amp, otherwise I'd just go down the other route and connect them directly to the TV.
Since the amp doesn't handle audio over HDMI, you will need optical cables to connect the PS3 and 350 to the amp, whichever way you connect them for video. The amp will automatically pick up the optical signal for the source you select on the amp, if you haven't connected the HDMIs through it. Otherwise you may just need to cycle through the 'input mode' (theres often a button on the from of sony amps for this)for each source and select optical manually.