Can someone help me decide between an amp and an integrated amp?

There is an inherent problem in having separates: money! No component you can name will sound very good just sitting there on its factory supplied footers with its factory supplied power cord and its factory supplied patch cord. That's just a fact. You need to upgrade the power cord, interconnect, and footers with cones. At the very least. Then there's the fuse, to name just one of several very well advised tweaks that can make a cheaper component sound much better than its much more expensive competitor.

Pick any component, at any price, connected to those freebie wires, its very easy to demonstrate you can beat it handily with the same amount of money in a cheaper component with better wire. And cones. No contest.

This holds true at every level and for every component. So it really comes down to, do you really like spending a lot more money for less total performance? Or do you really need whatever little extra flexibility you might get with separates?

That's the usual advantage of separates, flexibility. Only in this case while you would seem to be gaining flexibility in reality you're tying your hands, severely limiting your choices.

You're looking to upgrade to Maggies. Okay. Whatever. Everything said above applies here as well. I decided long ago to not consider difficult to drive speakers, not because they might not sound great, but because of exactly these kinds of constraints they force on everything else. Years later when you inevitably decide to change and find yourself with a bunch of stuff that was chosen mostly because the speakers limited your choices, years from now well just maybe you will understand why I made the choice to avoid difficult to drive speakers. 

But hey, these are all your choices to make. You are well advised to leave my opinion, and everyone else's, out of the equation. All I'm saying is go into it with your eyes open.

Its elitist to acknowledge the fact that you can do better spending less by paying attention to details like power cords? Getting more for your money is elitist?

What seems to have you so worked up elizabeth is this:

No component you can name will sound very good just sitting there on its factory supplied footers with its factory supplied power cord and its factory supplied patch cord. That’s just a fact.

Well, that is in fact, a fact. Which in spite of what you seem to think is nowhere near the same as saying you are required to buy the power cord, etc. What it says is what it says. I find it helpful to try and read and understand what people actually say and write, and not stuff my made up prejudice into their mouths. YMMV.

@bradkava,
If you want to save space and possibly some money buy a good integrated amp with enough power to drive Maggies. With an integrated amp, you don't need to purchase interconnects for a preamp.
If you have space and funds then individual components are an option.
It's a matter of personal choice and no one but you knows what your preference is. I also should mention that I believe in the long run it's worth waiting in order to purchase components that are really good vs mediocre.
For example, this would do the job nicely: https://www.audiogon.com/listings/lis9die5-luxman-505ux-mk-1-integrated-amp-solid-state
I'm sorry to say I don't know if using your headphone amp would work as a preamp. I think we would need to know the specifics of the headphone amp. It would also be helpful to know a dollar amount you are willing to spend.