[Fungus]

I know that the O2 is very large and is considered transportable than portable. 
 
However I want to know if the O2 performs vastly better or just about the same but with more power than the C5 amp
 
And are either of the batteries user replaceable? 
 
How long does the O2s battery last? 

 

[gauchotodd]

I have the desktop O2 and the C5D and think it's the perfect combo. The O2 definitely does not perform vastly better, and even if I had the portable O2, I'd still prefer the C5D over it pretty much across the board for on the go usage. I think the O2 is great for super neutral, analytical setups, I use it with the HE-500 and would pair with the HD800 if I had them. I like the C5D with closed-back cans, it has an ever-so-slightly pleasantly warm sound (which is probably more from the cans I'm using with them than the amp), and the balance, bass boost, and volume are all wonderfully controlled.