....so I want to upgrade to a 1800 watt rms amp...
So there's no way to run a powered signal from my iphone 5 into just an amp, I'd need a preamp...
As mentioned the headphone output is designed primarily for earbuds and IEMs, maybe some high-sensitivity headphones - it's not the same as a preamp just because it has a volume control.
...I mainly plan on using my phone to play music...
... I also have a Fiio e7 amp+dac if that would be able to do anything?
The E7 meanwhile only has a lineout with the L7 adapter, not a preamped output, and I don't think the iPhone can use the E7 as a DAC - it can use it as an amp but what you need is to get the sound into the receiver or a preamp.
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What else is in your set-up anyway? What receiver is that and what speakers, also is it dedicated 2ch or 5ch? Because 1800watts RMS even if its powering a 5ch system is is any one of these: 1) an overkill 5ch HT amp, 2) an overkill PA system 2ch amp, or a 3) ****ty amplifier so full of crap it claims that much output on the cheap, cheesy sticker on it (here in Asia we have tons of "Alpine" car audio amps with a sticker claiming it can produce 3000watts peak music power output on the sticker, then you look at the box and it says something like 35watts RMS x 4).
If I get it right that you want to use your iPhone as source, and also to be able to manipulate the system volume without getting up and walking over to the equipment rack, you could try getting a dedicated "Made for iPod" DAC - check out the
HRT iStreamer.* You can even get the iPhone dock to keep it upright and hook up the data cable into that (see photo below),** that way navigating through the player app might be easier for you this way. Next, just get a bit more creative - use a much smaller amp with enough power (assuming yours is an old HT receiver with barely any real "high current" or "high output" capabilities, even a decent 2x50w rms stereo amp might be enough for you), like the
Dayton DTA-100a, put it on a table or a smaller equipment rack next to your listening chair, and hook up the speaker cables creatively (ie, keep them out of the way even as they run across the listening area, maybe even out of sight). I'd rather run long speaker cables than long low-level signal IC's so I'd explore using such an integrated amp instead of a pre+power amp
if indeed what you need is to have the volume control nearer to you.
That, or you can get a newer receiver with a better amp section (even entry-level receivers now have discrete channels, just not its own PSU separate from the processor as on some TOTL integrated receivers), then for your iPhone source, use bluetooth or - better yet - get a network capable receiver, hook up an HDD media server along with the receiver to your home router, and now you can use the phone as a remote without being limited to the whatever memory your iPhone 5 came with. I have a remote app on my Android, and use it to control MediaMonkey on my laptop blasting house/beach music when I'm in the kitchen, grilling or hanging out at the patio, etc. From what I read on manufacturers' blurbs, like Onkyo's, when properly set-up you can see the content on your phone much like when using a computer. When I was using the free trial versions, I just limit the playlist to the party music playlist and all I had was previous, next, play, pause and stop - just enough to respond well to, "What that?!" and "Dude I hate this song!"
*Before anyone brings up the Pure i20, I have no idea if the lightning to 30-pin adapter will allow his iPhone to work with it, but in any case the height of the support on the dock minus the adapter might make it feel clumsy
**Not exactly an iPhone or an iStreamer but basically the same idea
