Ti's will do all that you desire. I have them on my Sadowsky M5-24, and I think they pair well with bright basses, since they are little mellow. Great sustain for flats, you will like them on your Sterling. I used to have a Sterling fretless (I used Daddario nickel rounds mostly) and know Ti's will be great on that bass. TI's are particularly great in the mix (true of flats in general) warm and punchy.
Perfect! Thats cool! I'd like a set of mellow flats but I want them at not just sit there in the mix but to stand out. Like harris, even without boosting bass on the tracks you can clearly hear him. All other flats just seem like you have to isolate the bass just to hear them. The TIs seem like they are low tension, mellow, and stand out.