I've got a Tampa and a DMP3. The differences are surprising and subtle at the same time. When using a DMP3, or regular mixer pre, or a Blue Tube, I never felt like the sound of vocals was very "alive" regardless of the mic (GT tube mic, AKG2000, SM58, Octava MC012)- it was always kind of 2 dimensional.
The Tampa feels very "alive" when singing through it. I now use a standard SM58 through the Tampa. It felt like a dramatic improvement and vocals now seem more 3 dimensional.
I once recorded some
acoustic guitar through the same chain at the same time with the DMP3 and the Tampa. Based on the feel of vocals, I expected there to be a huge difference when I listened to each track. But there really wasn't that huge of a difference. It was only after I listened a few times that I heard that the Tampa is less "hyped" than the DMP3. Chain was Octava MC012 -> the two pre-amps -> ADAT.
A few people around here have said that a true test of a pre-amp is to record a 8 track song with it to see how the tracks mesh. I like the Tampa a lot and would buy it again, tracks just mesh better with it. I don't find myself always tinkering with EQ anymore...
Now that I re-read this, I'm not sure if this is a great answer to your question....