You might consider selling the Canon EF 50mm f/1.4 USM and EF 85mm f/1.8 USM and investing in the Sigma 50-100mm f/1.8 DS HSM Art. That would give you a very nice range of focal lengths with a prime-like aperture. You could use the EF-S 17-55 f/2.8 IS USM for the normal range work and then switch to the Sigma to cover your longer needs.