How to connect iPhone to PA system thru XLR jack

I want to play an iPod, iPhone 3G, Zoom H4n digital recorder, and a CD player through the PA system in a room. The only input jack available to me is a female XLR jack on a wall plate. All my devices have a 1/8-inch (3.5 mm) TRS stereo female jack while the XLR wall jack is a mono input normally used to connect a microphone to the PA system. Obviously I need to sum the stereo signal into a mono signal. But do I have other requirements?

It is possible that the XLR wall jack has 48-volt phantom power. If I connect an iPod or other device, will the phantom power damage the iPod?

Do I need to worry about impedance matching?

Do I need to worry about matching the voltage of my devices to the XLR input? Is the output of my devices -10 dBV line-level? What voltage is the PA system expecting?

There are simple converters that will physically connect my device. I can get a converter that converts 1/8-inch TRS to ¼-inch TRS. Another converter will convert ¼-inch stereo TRS to ¼-inch mono TS. And a third converter will convert ¼-inch TS to XLR. I haven’t found a converter that will do all three conversions but I think it can be done with 2 converters.

I already own a Whirlwind IMP2 direct box (DI) but don’t know if it’s useful for this application.

There are also more expensive devices such as

$160 Pro Co iFace

$130 Whirlwind pcDI

$85 Whirlwind podDI

What is the best solution?