On occasion I myself did comment on Tautech's tenacity in promoting Siglent, where I felt he went a bit overzealous ..
But in this occasion, I will support him and say that SPD3303X-E is probably best buy for OP... Other one would be Rigol DP831, (more money though), that has 3rd channel that is also fully regulated and settable like (0-8V / 0-5 A). Rigol has Ethernet, and supports programmed ramps, recording of measurements etc.. Also via SCPI, you can read measurements from PC like you would from meter.. I believe SPD3303X-E also has some of those capabilities.
I have Rigol DP831 and it works very well..
Both can be easily unlocked to more expensive model with increased resolution and capabilities.
Jan, laboratory PSU is not simple project, and by your own estimate and by what knowledge you demonstrated, I think you are not in a position yet to design and make safe and high quality PSU of the type you would like. By all means, make it your learning project, but if you want reliable workhorse PSU you'll have to buy one, either one of the two I mentioned, or maybe and used old brand name one, in which case you might get a broken one that you will have to repair.
Regards.