For knocking up studwork, skirtings, cutting mouldings ( or any timber lengths ) a mitre saw quickly pays for itself. I bought my first for about 400 quid 22 / 23 years ago, just a 216mm dewalt with little legs that fitted onto rails that slid into the base..... it lasted around 14 years and when i replaced it, it was just brushes that failed, but i bought a new one with zero play. It had earned its money many times over and by the time i bought my second, they had dropped to about 250 quid for the same size!
I can see that the tracksaw will pay for itself and will do a neater job than my circular saw and straight edge. The rail clamps are great.... to be fair, it is a good system for site carpenters and the hobby guys.
The mft thing, well we'll see. I havent used one. I can see the advantages of say the hinged rail and being able to quickly get square cuts using the dogs etc.
The rail squares? Theres a lot of choices, ranging from 20 quid up.
If, in practice, a rail square is within a mm over 2.4, its worth the 240 quid in the long run..... but itd have to be that accurate or better. Of course at that length a parallel guide is the right tool, but how far do you go?
For me, the torsion box is worth doing. I often cut sheet material on site and if the benches aren't properly level and supporting the sheet adequately, it often results in the saw binding. I usually catch it before it gets close to kickback ( i can feel it bind ) , but the flat top will eliminate that and give me the bonus of cutting squarely fast using the dogs and fence on anything probably 200mm less than a full sheet size...