Sounds like you're getting yourself into quite a box. It's difficult to offer precise suggestions, since you haven't listed much about the application you're attempting to do. However, a couple of thoughts:

- On the subject of normalization, you can limit the impacts on the user community through a careful migration path that includes views to replace existing denormalized tables. While not a quick fix (and difficult to wean people off then views then), it'll allow you to proceed with the most valuable changes.

- Two Terabytes is a substantial (but not unmanageable) data source. Consider carefully typical usage. For example, you could use partitioned views (i.e. by month), but make sure you cluster the tables by the criteria most often queried against. Slicing up your IO often produces the most dramatic performance gains.

- Reconsider the SQL Standard / Enterprize question. We've all had to deal with the budget issue at some point, but what type of FTE support will be needed performing the optimizations manually, vs using the extra features supplied with Enterprize. It's all about cost / benefit.

- You don't say what type of reporting application this is. If it's a data warehousing application (which I suspect it may be), Consider implementing Analysis Services. Of course, the disruption and change is much higher, but the potential benefits are also larger. Note: Again, partition support is in Enterprize, so you must move up a version.

- Reconsider the granularity of the data, particularly older data. If you summarize it, you'll get compression on disk, IO, etc.

If you get a chance, post your schema. There may be some easy to do optimizations you've missed.