TL;DR: The Impact has 24 channel faders with programmable scribble strips, but lacks the Expression/Performer per-channel Gain/Pan encoders. If that's not enough faders , you get 6 more with the Performer 3 or Expression 3 (if you don't care about scribble strips). Don't buy a Performer 2 or Expression 2, the Impact is cheaper and better.The Soundcraft Si Impact is a worthy update of the Soundcraft Si Performer 2. Like the Performer, the Impact has programmable scribble strips on all channel faders and selectable bandpass/shelving filters on Hi and Lo EQ bands. However, the Impact has 32 XLR inputs on its back panel, compared to 24 on the Performer 2. The Impact also has 24 channel faders compared to the 22 channel faders on the Performer 2, but the Impact lacks the rarely used DMX controller features of the Performer.The one downside of the Impact is its lack of per-channel Gain/Pan encoders. Virtually all other features of the Impact and Performer 2 are identical, including the touch screen, which takes up more real estate on the Impact, but works exactly the same as the Performer. Aside from the Impact's missing row of Gan/Pan encoders, the only significant reason to prefer Performer over the Impact is the 30 channel faders offered by the Performer 3.As for the Expression, it has all Performer features except the programmable scribble strips, bandpass option on Hi and Lo EQ bands, and the DMX controller. Of these, the lack of scribble strips is IMO the crucial flaw of the Expression. One of the standout features of the Soundcraft Si consoles is their brilliant implementation of motorized fader banks, which enable you to switch fluidly between the board's 4 input channel banks, 14 submixes, 4 effects busses, and 4 matrix mixes. But what makes this elaborate mechanism practical is the instantly updated text labels displayed on the channel scribble strips. Without that essential feature, Expression users must resort to manual aids to recall which inputs are routed to each of the faders in each fader bank.What makes the Impact and Performer models so flexible is the ability to quickly map ANY input channel, submix master, or VCA to any channel fader on any of the four fader banks. This allows you to quickly group channels and submixes in any order you prefer, any time you feel like it. No awkward eight-channel block boundaries, no artificial fader-assignment limitations, no deep dives into nested menu layers - you can literally put anything anywhere you want it. The Soundcraft Si was one of the first full-featured digital consoles on the market, and while its utilitarian touch screen is outdated, its ingenious design and intuitive user interface have set a standard that remains best in its class.