Upgraded/Hotrodded Dehavilland Ultraverve?

Has anyone upgraded an Ultraverve or heard one? If so, what did you notice as an improvement? I am referring to both tubes and internals. And, how did they compare in your system with other preamps in your system? I am hoping to listen to an Ultraverve soon (stock unit) as Kara recommended that over the Mercury series for my system.

This preamp is well under my budget, which is why I was considering the upgrade route if I end up getting it.