I've heard the W4.. it's a fantastic phone. I had only one issue with it.. the bass came across a little too soft for what I expected from a 4-driver BA. The control, texturing, and accuracy was top grade.. but I wanted a little more energy from the bass.. especially for a phone with two dedicated bass drivers. The quality of the bass though was incredible. Treble compared favorably to the quads and the midrange was quite impressive too (I'd call it a draw between the quad and W4).. well balanced and highly detailed.. Personally though, I'm enjoying the quads more and don't regret my decision one bit.
There's very little not to like about the W4, if it matches what you look for in a sound sig. If I was forced to choose a top tier universal, the W4 would be it (but honestly, the GR07 is the last universal I'm interested in cause I enjoy it so much).
Re: the FA-011.. as you said, is all together a different beast vs the quad.. The 011's wide-U shaped sig is quite a change from the slightly mid-forward, more balanced, relaxed nature of the quads. It's actually a bit of a shock going from the quads to the 011 and vice versa cause the treble is so different.. the 011's treble is clearly emphasized, very very crisp, sparkly, and bright.. obviously tuned for emphasis.. the 011's bass feels softer and less controlled in comparison to the quads' bass, but it's still excellent nonetheless. It doesn't have the authority, speed, detail, or nuance the quad's bass possesses. I love the 011's midrange.. it's very natural sounding and has good timbre, it's not recessed or forward, it's quite well placed, IMO.. it may sound that way to some since the bass & treble has emphasis. I'm still burning the 011 in so I'll hold final judgement.. but these sound better and better with every hour.
Between the 011, 598, & 003.. my "full-sized phone" appetite is full.. heck the 003 would be enough for me, I love the sound of those phones. As with IEMs, the next full size phone I invest in will be in the 1K range and when I have the appropriate amp/DAC in chain to take advantage of it.