badhabit, your comments bother me. I too have the Woo WES and Stax SR-009.
First, you already observed that the RCA inputs on the WES are a joke. Not worth even talking about due to all the noise they generate. Woo should not even be promoting this feature on the WES, it's that bad.
Second, you should not be connecting a 3.5mm output into the WES. The sound quality degradation would make it pointless. Put it this way - your Woo WES and Stax SR-009 are like the engine and body of a Ferrari Italia. Now, for tires, you are using no name Walmart brand. Yeah, the car runs and it's still fast, but the handling is so far below what it should be, you'd be better off with a Toyota FR-S and its stock tires.
So if you're going to use a DAC or source with a 3.5mm output, you might as well get a $1K amp instead of a $5K amp, because EVERY ITEM IN THE CHAIN needs to be in the same caliber, or your entire system will sound like the weakest link.
The CHAIN consists of: A/C receptacle (or even further back to the panel) -> A/C cord -> power regenerator/conditioner -> source -> cable -> DAC -> cable -> Woo WES -> Stax SR-009
I tried to rationalize and wonder if a top-end DAC will really be necessary; but after much studying the answer is yes. Especially with the WES and SR-009 which is the most revealing rig you can buy. So if the source is not top-tier or the recording sucks, or the DAC is just so-so, you will hear the impact on the sound quality much more than with a lower priced rig.
So seriously, think about spending $5K on A/C/cables, $5K on source/DAC to go with your $10K WES and SR-009 combo. At a minimum! This is a ratio that I've heard used before (i.e., 1/3 on source, 1/3 on amps, 1/3 on output)
I'm still not a believer that some things are worth the money (there have been all those listening tests comparing custom cables to coat hangers, for instance...), but I did opt to go with a high-end DAC in the end. I'm using cheap cables from amazon, incidentally, and I couldn't be happier. I'm not using a power conditioner beyond a cyberpower battery backup unit, which of course isn't really designed for audio.
I think the main benefit of having a good DAC for me, though, was just getting the XLR outputs. The key thing with the WES is that the RCA inputs are, like you said, absolutely terrible.
I didn't make any sort of thorough comparison (I would have needed to buy more equipment on blind faith...), but I connected an ipod's 3.5mm output to the inputs on the DAC1 and then routed through that to the XLR outputs to the WES. That should have sounded terrible, right? I really couldn't perceive any sound quality degradation. I'm sure there was some, but when I listened to my friend's music all either of us could think was "wow, that sounds amazing". Pulling up the same songs from the computer and outputting it directly through the DAC1 sounded pretty much the same, albeit with a slightly different tone perhaps... different, though - not "worse". Likewise, I chained my 'cheap' ODAC through the DAC1 and I couldn't really tell much difference. Outputting directly through the DAC1 did sound slightly better overall, but it was quite subtle.
On the other hand... comparing the way my WES+007 sounds to any dynamic setup I've ever heard? No comparison. It sounds drastically better. So, in terms of bang for the buck, I have to say that I don't think it's pointless to get a cheap DAC (provided, again, that it has the outputs that are needed for the amp) or cheap cables. You may get some improvement with a more expensive one, yes... but is that improvement so significant that it renders otherwise excellent equipment pointless? I don't think so. From all the reviews I've read, sometimes the primary difference you hear between DACs differing in price by thousands of dollars is simply a change in sound signature that is very subjective. Depending on your setup, you may not even want that kind of change. You lose some quality at every step in a lossy chain such as an audio setup. Replacing some of the components isn't pointless without replacing all of them. If the headphones themselves and the amp have the biggest impact on sound by a large margin, then why pay even half that amount of money on the rest of the chain? I know we all have upgraditis sometimes in this hobby, but... :)
Oh, I'm with you there... I heard the 009 and the 007 paired with the WES, and I decided to buy the 007. The 009 was just too revealing. It reminded me of my Etymotic IEMs in that regard. Everyone's ears are different, so I'm sure some people perceive the 007+WES differently, but for me it's just right.
Anyway, I continue to absolutely love my setup. I'm sure if I attended some more meetups and heard some different amps, I might decide that some flavor of the month (not that there are all that many electrostatic amps, though...) sounds slightly better, but I really can't imagine anything sounding that much better.