Well i tried the rega fono mm mk3 against the roksan blak built in phono today and thought the blak sounded better.
To be honest i was hoping the fono would sound better, the reason i say that is because i want to invest in the sweet vinyl sugar cube and to hook that up to my system i would need an external phono stage, my rega turntable does not have built in phono stage. Might try the schiit mani and see how that goes.
Well if the in-built one is good, you don't really "need" an external one. The Mani is great, imo, and even better with the Swagman Labs PSU. But I don't know if a budget phono pre can be an upgrade over the one in the Black. Maybe Simaudio Moon 110lp v2 upwards.
Whereas you could just spend the money on new LPs.....
To my mind anything bad enough to require the Sugar Cube is going to damage your stylus or simply get worse so not economic to play in the first place particularly if you have to facto in cost of an external phono preamp as well.