Before running the gambit of upgrade-itis, are you certain you're really unhappy with the SE535 bass? It's not that there aren't bassier headphones, it's not that you may not have different preferences for different sound signatures, but the trouble with IEMs, when a well rounded headphone gets a comment like anemic bass the question that has to be asked is: "just how anemic would you describe your bass.'
It's not an IEM for bass-heads, but it's a very well-rounded IEM, along with W4. The sound signature reminds me very much of my Senn HD650 on slightly warm tubes with the nice liquid mids, which is why I like the 535's. While not a "basshead" can like, say, Denon, or even some Ultrasones, HD650 holds its own with realistic bass. Some argue it's even boomy.
Are you looking for more of a Denon-like bass from your IEM, or are you not getting all the SE535's bass due to a bad seal or other ergonomic issues? What tips are you using? Are you sure the seal is tight? Are you sure they're fitting into your ear correctly, etc?
When I first got my SE535's I thought they were lacking some bass I expected, even though I thought I had a good seal. With some experimenting I learned that the olives (black foams) weren't sealed as well as I thought...getting them a little deeper solved that problem and the bass appeared.
Of course if you have ergonomic issues preventing a good seal, it may still mean it's the wrong IEM for you, of course. But it's an important thing to consider when you're already at the high-end of universals and find it's lacking something...especially if it's bass.
To argue the opposite side for you, though, the nature of BA drivers is to not be overwhelmingly bass heavy. To my opinion, for what it's worth, the bass is very natural and realistic. For someone who craves heavy bass, it may seem light. The only way to fix that is to move away from BA and back to ported dynamics, but you'll sacrifice some clarity automatically in that process.