I have forgotten to mention that I purchased Fidelia because I wanted standard AU/VST plugin to create warm tube sound as all my audio gears have neutral sound signatures. Only Fidelia and Pure Music accept standard formats (AU/VST) audio plugins (pick your audio preference here: http://www.macosxaudio.com), hopefully Audirvana Plus will follow suit. After listening to warm tube sound for a while, I realised that it does not suit all music genres (good for vocal but bad for instrumental), thus my preference right now is still neutral and transparent signature. Pure Music requires iTunes to work as plugin and there is no standalone version.
Thus if you want high fidelity without additional audio processing, go for Audirvana Plus and if you need tweaking in sound profile with AU/VST plugins, go for Fidelia (advanced mode). Audirvana Plus, Fidelia and Pure Music are the three alternative media players that have impressed me most but Pure Music need iTunes to work though it has the most features among these media players.
Could you possibly elaborate a bit on the plugin you use for "a warm tube sound" ? I use Fidelia ... and dabble a little with the plugins -- but I do not understand ... are you using something you found elsewhere ? (the plugin)