iPad directly into Amp - okay idea? or bad idea?

I'm beginning my journey towards building my first audio system, and off to a great start with a pair of B&W CM9 S2 speakers. Next step - I need to power them with... something. I've found several vintage McIntosh amps available (like the MC 2105 & 2205). I was targeting around $1-1.5k more to get my system up and running, and these would consume that budget.

I'm considering pulling the trigger and getting one of them and plugging my iPad in to play music. Then I'll save up for a little bit until I can buy a proper tuner (I need a tuner next, right?). I get that this isn't ideal, but I'm wondering if it's bad for any reason? 

Additionally, I'm not sure about the nuances of how an iPad's headphone jack increases/decreases volume. I vaguely recall from long ago that plugging an iPhone into a tuner's component input sounded bad unless the iPhone volume was on max. Is this true? And if so, would that mean it would sound bad if it were anything less than full volume going into the amp? Which would almost certainly be too loud, correct?

And if I'm totally off track here, then how I can make music on my iPad play on my speakers for around the same price? 

Thanks in advance!