Objectively you can achieve better dynamic range by 3dB when doing a design with dual chips.
I own an SMSL DO300 EX after getting rid of the DO300 that has a couple of issues when playing DSD (It applies too much gain to DSD, over +6 dB which is the standard, resulting in some distorsion and boomy bass, and DSD inverted channels vía I2S which is not corrected by inverting I2S channels on the configuration menu), and I much like the sound of the DO300 EX over the DO300.
I find the DO300 analitycal and bright for my taste. It may be more truthful to the source than the DO300 EX but for the time I've had the DO300 (around 9 months) I felt something was missing or at least not for me.
The DO300 EX corrects the issues when playing DSD that the DO300 has, It sounds smoother, more easy on the ears to me for listining sessions.
But beware, It may be a matter of sinergy with the rest of my equipment, a humble but fine sounding Marantz PM 6007 integrated amp and B&W' DM 601 (yes, the first series, which I bought in 1996, filters were changed around 4 years ago), or maybe my hearing as I'm 50 and have been suffering of tinnitus for around 8 years.
The fact is that the DO300 caused be listing fatigue after 40 minutes or so of listening, and the DO300 EX doesn't even after listening of for over 3 hours.
By the way, the DO300 EX states on its instruction manual that features TWO AK 4499EX converters.