Before I begin: a particular feature of players that significantly effects etymotics is output impedance. This significantly restricts your choices. I mention it quite a lot. They are also super-sensitive and so much more likely to hiss with poorer kit. I find hiss significantly detracts from a lot of the music I listen to and hinders 'total immersion'.
A Sansa Clip+ or Clip Zip (or the original Fuze, not the Fuze+) will give you hifi audio with these iems. The bass is a little weak on the etyomotics but the Sansas have a decent EQ that doesn't distort like the ipod's terrible EQ. The Clip+ has a weak power button; maybe the Clip Zip fixes this. The Clip+ also runs the 3rd party Rockob firmware, which opens up new worlds and has great EQ. EQ is used constantly by professional audio mixers/audio-engineers in making music, so don;t be afraid of it so long as it is a quality EQ (not ipods and not Windows Media Player which are bad).
I may be wrong but there is a significant possibility that modern laptops using off-the-shelf audio cards are producing hifi audio. If this is true it is perhaps because audio has matured to the point were even a cheaper implementation satisfies the requirements for perfect 2 channel audio playback. I can't tell you this for certain since it would require a more scientific approach (ie, ABX/DBT testing) but using the famous O2/ODAC combination (which is hifi) with my etymotics, I cannot tell the difference between it and my Realtek and Sigmatel equipped laptops/computers (apart from a trace of noise) of the last 6 years. My older pentium 1.7Ghz laptop, however, is poor and hissy.
It does seem like phones tend to be equipped with sub-hifi, even poor, audio. The Galaxy S3 does very poorly when measured using high-end audio measurement kit. It seems that if the chipset is not 'off-the-shelf' then it is a custom design and may have deficiencies that a mature, but cheaper, chipset would not have. I would personally stay clear of Wolfson equipped kit as it is likely custom designed. Apple kit if near-hifi but often a poor match to your etymotics as they often have high output impedance (Mac Books and ipods) which is an electrical quality that significantly effects low ohm headphones and particularly balanced armatures. The newer Iphone 3s and 4s are fine (and hifi) for etymotics, but not the iphone 5 (output impedance issues, it needs to be 2 Ohms or less).
Since the Clip+ is famous for its audio (and gives hifi in scientific measurements and has very low output impedance) I would get that first and then do a simple comparison between it and your computer. If you can't tell the difference then you can save yourself some money. if you can tell the difference then you may need a DAC/AMP combo to bypass the onboard audio. The cheapest way I know to do this is to get the Behringer U202 DAC and the FIIO 5 amp. It's not totally ideal but it will give you near-enough hifi that could power some fairly power-hungry phones if needed. The reason for the amp is not power but to correct a high output impedance of the DAC that will damage your HF5 experience. the Fiio 5 can also be used to correct Apple output impedance issues. The FIIO 5 is just a touch off being hifi; an amazing bargain like the clip+.
Alternatively you could get the Schiit Modi Magni combo which is a lot more money but the specs suggest hifi audio. If you want to go for a proven purist solution then the O2/ODAC is even more money, but I reckon you'll be happy with the Schiit offering. I would look for independent verification of those specs, however. You could compromise with a Schiit DAC and the FiiO 5.
A final note on hifi: increasing the bass on these phones is important to most of us, other than purists, and compensates for human insensitivity to bass. I would suggest doing this moderately, perhaps just 5dbs. It's easy to get wonderful crunching bass but doing that will also distract from the main music. Ideally, a rockboxed clip+ would allow you to use the parametric equalizer with a setting of +9db at 30Hz Q (width of the effect) =1.4. As with most phones, etymotics have a spike in the treble caused by inner ear reflections/standing-waves. It varies between 7.5Khz to 8.5Khz at about 8dbs, depending ont he individual. It's a good idea to EQ this out with rockbox. You need to find the Head-fi mega thread by
Piccolonomek on equalisation. For this I would advise ignoring his advice on using pink noise to determine the EQ width, which generally ends up being too wide, and go for a Q=6.4. this spike is not a critical issue, but it can be fun to know you've reached the ultimate. (Something that tripped me up: other EQs use BW instead of Q for width; they are not the same and you'll need to convert between them).
