Hi, no responses to my post so I thought I'd at least better try some of the other threads needing answers!
I don't think that there are any easy answers to your question, not least because there are an awful lot of options out there and precious little opportunity to try and compare. I also think that many people try new components in the audio chain - of which I think DACs are currently THE most important link - but don't hear (all) the improvement that they might, because the resolving power of their other components doesn't let them hear the extra detail (say) that the new DAC lets through.
I can however give you some general advice (from the point of view of a passionate hi-fi fan with limited finances):
[1] Enjoy what you have - the music itself matters more than anything else, and a later upgrade may well let you rediscover your collection all over again anyway. So concentrate on your collection (or playlist?), the replay equipment is just a means to an end...
[2] Take time to understand what real improvements sound like to you, and what differences this makes to your experience of the music. Get out there and listen to live music, especially unamplified music in sympathetic venues (i.e. where the music isn't competing with other sounds, like bar-room chatter, say. If it is, get close up!). I also throroughly recommend attending Hi-Fi shows - they are fun, great value for money, and a chance to discuss things with both punters and professionals. Get to as many closed-room demos as possible. Unless you've nearly made up your mind, don't go "shopping" for stuff you might buy, but aim to hear the best sound you can and especially go for demos of equiopment that takes a very different approach to your own. Make sure you know what music is playing. Make notes, but only when something 'jumps out at you' (good or bad). Talk to your hosts, make requests for tracks but check what they've got there first. Try headphone equipment...
[3] On that last note, I think that headphones provide the key to evaluating source equipment or DACs. While I can't afford the kind of high-end systems that I listen to at shows, many of them _are_ really good and would show up the differences between DACs quite readily. However, I can afford a decent pair of headphones and the recent trend towards combined DAC / headphone amp devices, and following my own advice (as above) has led me (eventually) to buy such a device (see my thread "iFi nano iDSD - first impressions"). Through my Sennheiser HD600s, playing tracks from my PC at home, I'm hearing the best sound that I ever have using my own equipment. (Portable use with Sennheiser IE80s also gives extremely high-quality sound, but I've yet to iron out playback glitches from the Android App.)
This last point is the key, I think. Unless you're the kind of person that dislikes using headphones, then the affordability of the relatively low power amplification and the 'phones themselves, means that you can have both fantastic playback quality and the means to very effectively audition a DAC or other source. If you can relax about the process then it just be more fun: after all, if you're not convinced then just go back to point [1] and enjoy the music until something convincing does come along!
You're not going to get the _final_ answer from this or any online forum, because the experiences of music (through any type of equipment) are yours alone. In the end, it's your persistence and willingness to ask, listen and get out there where you can evaluate for yourself that will get you the best result. Good luck.