I used a Speedbox 2 on my Debutt III and 2 Xperience and in both cases sound stage became more 3d, bass articulation was tight and it yielded blacker backgrounds. I use Proac and B&W speakers which are both fairly revealing so the differences were clearly audible.
That said Pro-Ject has excellent speed and pitch stability in stock form unlike certain older Regas and a few other brands. I used Linn tables for 2 decades (Lp12 and Axis) and those were always spot on for speed and pitch so I wanted the Pro-Ject to be comparable. Of course the difference you get from something like a Lingo on a Linn is far more dramatic, as it should be for that kind of money. But I think the effect of the Speedbox is easier to hear than say the TT PSU that I use for my Rega P5.
I have not tried the better Speedbox SE but the base model is definitely worthwhile and very reasonable price wise.
That said Pro-Ject has excellent speed and pitch stability in stock form unlike certain older Regas and a few other brands. I used Linn tables for 2 decades (Lp12 and Axis) and those were always spot on for speed and pitch so I wanted the Pro-Ject to be comparable. Of course the difference you get from something like a Lingo on a Linn is far more dramatic, as it should be for that kind of money. But I think the effect of the Speedbox is easier to hear than say the TT PSU that I use for my Rega P5.
I have not tried the better Speedbox SE but the base model is definitely worthwhile and very reasonable price wise.