Dan, it's called the Khan VTDI now. Obeid Khan, who used to be an engineer at Ampeg, makes it. Me, I'm sticking with the REDDI. Served me well for a year and a half so far and it's freaking amazing, but nothing at all wrong with the SVT-DI.
You could run the SVT-DI from your line out in your amp, sure. Some might argue it's overkill to do so, though, and many soundmen would rather you let them control the tone and not involve your amp. Never was fond of that type of soundman because they often end up ignoring what you want for a sound, plus they tend to get mad if you change your sound or volume during the gig. I much prefer soundmen who roll with whatever you want.
Ampeg Portaflex Club #1