Shadow 7 said:
The Art MPA Gold is supposed to be better (with after market tubes). I got the DMP3 over the VTB-1, but I've never had a VTB-1 to know if it's better. General consensus seems to suggest that it colors the sound too much. The samples of the Art with Tube upgrade compared favorably over preamps 3x's it's price (including replacement tubes). It really depends on what you're going after? That transparent sound or something different?
The VTB1 is an op amp based preamp with a tOOb circuit and a blend control that allows you to dial in how much "tOOb" sound you want. If you dial the tube blend control all the way down to where it says "SS", it takes the tube out of the circuit completely, leaving you with a fairly clean preamp. If you crank it all the way up, yeah, it probably colours the sound too much. I don't use it.
Seriously though, the Art, the Studio Projects and the DMP3 are all in the same league. Splitting hairs over one or the other won't get you too far. An SM7 needs lots of clean gain and the Studio Projects can deliver it. The Art is also supposed to be able to deliver it. I've had my VTB1 cranked to the hilt and it's quiet. I don't know about the Art.
If you want to get into a different league, start looking at things like Sebatron, Grace, Sytek, A Designs, Daking, Great River, API, Neve, etc...
You get what you pay for. Once you get up to around 500 bucks per channel or more, you should hopefully have something that gives you more of a 3 dimensional soundscape and starts to really open up the sound of your dynamics and ribbons. The AEA TRP might be an exception as well as Sytek.