You're never going to get a like for like replacement. That is probably the best EF-S lens Canon have ever produced. The Tamron gets close in terms of sharpness but the build quality is nowhere near that of the Canon. The Sigma has better build quality than the Tamron (IIRC) but isn't quite as sharp.
Do you have a particular focal length you prefer to use ? If so, maybe a wider prime and 50mm f1.8 may fit the bill better ?
Steve