questions about streaming source for a headphone amp


I've owned some decent headphones in the past but I want to move up in the headphone world (Clear, 800s, Arya and a suitable amp). Basically, I'm trying to figure out if getting good headphones means building an entirely new system. I've been researching headphones and amps, and when I came up for air I realized I need a suitable source....

In the past I've plugged my headphones (e.g., Sennheiser hd600, Grado RS2e, etc) directly into my phone or laptop or preamp, and it's been fine. I'm guessing, though, that something like the 800s needs a dedicated amp. I'll mostly be streaming music and I'm not especially keen on buying a new streamer and dac as well.

1) Would it make sense to do this, using my current stereo system: streamer > dac > (preamp?) > headphone amp? My preamp has two sets of "outs"; my dac has both balanced and unbalanced outs. I have no idea if I can run cables from either the preamp or dac in two separate directions. I know this is newbie stuff but would I have to turn off my speakers (at the amp or preamp)?

2) I'd like the source to be consistent in quality with the headphones and amp, the whole weakest link thing. I know this gets asked all the time but is an iPhone or MacBook an appropriate hq source for a good heaphone/amp combination? In that case, to stream hi-res, would I use an external dac (Audioquest dragonfly??). It feels a bit strange to me to spend $$$ on a headphone/amp combination and then stream the music from an iPhone via a portable dac. 

I'm interested that there aren't more headphone amp/streamer combinations. The Naim Uniti Atom HE looks cool, but not inexpensive. (The Aurender A30 ... $$$.) 

In short, how do people stream music through a headphone amp? Do you simply have a dedicated streamer and, if necessary, dac? (My son has a bluesound node I could experiment with.) Do you use your phone or laptop through an outboard dac? I'm sure I'm missing all kinds of things here... 

Thanks! 
northman
If this is for a desktop setup, then all you need is a USB DAC + headphone amp.

JDS Labs makes great performing gear (Atom+ amp and DAC) for a reasonable amount of money.

Currently I use a Benchmark DAC3 HGC with my PC and use foobar2000 to play tracks from a shared folder on a Mac mini. Works really well.

Hope this gives you some good ideas.
I'm interested in using my MacBook and I'm glad to know that many do so. Does anyone have any obvious ways to bypass the laptop's dac? It looks like I'll need to use a USB connector of some kind ....
Yeah, it’s just that a laptop is a noisy music source that significantly affects the digital signal.  I’d get an Apple USB 3 adapter that bypasses the MacBook’s DAC and gives you a USB connection, and into that I’d plug an iFi iPurify3 that’ll largely clean up the noisy signal.  Then it’s a matter of choosing your headphones and the appropriate headphone amp/DAC and you’re good to go in any room.  I have a Dragonfly Red that does work well, but that’s not powerful enough to get the best out of the headphones you’re considering although it may still be viable if you need/want to go truly portable at some point.  Hope this helps.