Massive Exchange 2003 servers is just naturally bad workload for vPower (since Exchange 2003, Microsoft has reduced Exchange I/O requirements a few times both in Exchange 2007, and especially in Exchange 2010 - one of the major reasons why we upgraded, btw).
Your current storage is certainly much faster than any inline deduplicating storage mentioned above (pretty much any raw storage is much faster than deduplicating storage). Typically, you are not able to run SureBackup from any inline deduplicating storage. So one thing you should not hope is that this new storage will improve vPower performance. ExaGrid is different though, as it does post-process dedupe and features raw disk landing zone.
I believe ExaGrid's main differentiator is expandability (thus "grid" in their name), but you'd better check with them directly.
At this time, we do not plan specific integrations with any backup storage - we like to remain storage-agnostic, and happy with the current performance of writing to those boxes anyway. While integration will not help with vPower performance anyway, because it does not accelerate random I/O.
Regarding best settings for writing to dedupe devices, they depend on device - most vendors provide integration guides, and their recommendations is usually different from ours because of different goals
anyway, there are plenty of existing discussions regarding this here on these forums, so please just use search to find those.