How so?
"Bass bloat" is a subjective interpretation and an over-broad generalization. If the headphones have a rise in impedance there will be an increase in amplitude there as Zout also rises. That doesn't mean "bass bloat" and there is not a universal increase in bass for all headphones/IEMs as Zout rises; it depends on the headphones and their impedance - there is not a single good reason I can think of for in-specificity about this. There are also many headphones for which this isn't really a necessary consideration (because they either don't exhibit a significant FR change, or don't exhibit a noticeable FR change). Current limiting is another discussion entirely, but if the amplifier can provide sufficient power for your target output (sensitivity will tell you power-to-SPL; safe levels are ~85 dB and lower, but you should factor 10-20dB of extra head-room so aim at something like 100 dB) it's nothing that needs to be "worked out" - if there's sufficient power, there's sufficient power. And what exactly do you mean by "and etc" - what else do you mean to talk about?
Such as?
Why not? More information is always better, and it's not like this is spoken word - folks can come back and read or re-read whatever they want. Let's not tear "OP" apart like a paper doll based on myriad assumptions.
Headphones (or speakers) are absolutely the most important part, the amplifier is (generally) dictated by the headphones and in many cases will be "next most important" (I like that "amplifier is an extension of the headphones" idea/analogy). Sourcing could be said to matter until it doesn't - eventually you will reach a point where the headphones (or speakers) are ultimately the bottleneck. With a lot of digital media (and associated sources) this isn't so hard to do, but with analog content it may be unattainable or require significant equipment to attain (e.g. FM radio will never be CD quality, and very revealing/good sounding cans (or speakers) will reveal that, but a quality FM tuner is still a lot nicer sounding than a clock radio).
I don't know that one, so I can't comment on it. But I would say that generally you're better off picking an amplifier to go with a set (or sets) of headphones, as opposed to picking an amplifier and then finding headphones after the fact. In other words, what do you have (or are you going to have) and then look for an amplifier that serves that. Combined DAC/amp units can be a very efficient way to deal with digital sources, as long as all of their functionality suits your needs (there's a lot of them that only take USB input, some that only take digital inputs, etc - not so useful if you also want to hook up a turntable, but no problem if you're just plugging into your laptop). If you're going with a device that will also work with a computer and act as an audio interface (e.g. something that plugs in via USB, FireWire, PCI, PCI Express, etc) you should also do a cursory search for driver problems or other quirks - the nicest hardware in the world can be brought down by bad drivers, and that's nothing you probably want to deal with.