What are your desires in the upgrade ? Bottom end or transparency / resolution ? In my experience going for transparency / resolution AND great depth/bottom end in a single package means big $$$$. That's why I recently added a REL strata sub to my Densen / Spica Angelus combination. The spicas have a lovely mid/treble, but couldn't drive the low end. The combination is fantastic ... I'd say better than the Kef 103s which a friend has.
If it's mainly for transparency then the AE1s (mentioned above) are very good, and proacs might work well. Also try out Epos if you can find them. I've always liked Epos, but never heard them with Creek. However the companies are closely tied now, so I wouldn't be surprised if the products work well together. Then there's always the Spendor 3/5. (Sorry for my obvious Brit bias ... it's what I am most familiar with, being a Brit myself).
If it's mainly for transparency then the AE1s (mentioned above) are very good, and proacs might work well. Also try out Epos if you can find them. I've always liked Epos, but never heard them with Creek. However the companies are closely tied now, so I wouldn't be surprised if the products work well together. Then there's always the Spendor 3/5. (Sorry for my obvious Brit bias ... it's what I am most familiar with, being a Brit myself).