unicorns can go bigger - 342hp
I would suggest just starting with a big rack (168hp by 4 rows is more than big enough) and work out what modules you want and what modules you need to support them, then get that checked by experienced modular users - by starting a thread with the url of your public rack for example (I think you can just comment on it) - this often takes several iterations and then once that is done, add a bit of space and power headroom for future expansion - add a further 30% to the power and then find a case or cases that satisfy both the power draw and the hp requirements
this way you can ignore the constraints of the case and power and concentrate on what you actually want to get from the modular and what you need to actually achieve it - it also stops you buying too small a case and then having to go and buy another one in 3 months when you realise that you "need" Maths (for example) and you only have 12hp left
good starter sizes for eurorack cases are 9u * 84hp (Doepfer), 6u * 104p (Tiptop Mantis) or 6 * 140hp (b-company go)
the doepfer and tiptop cases have been around for quite a while and have proven themselves to be solid and reliable cases and power supplies - the b-company one seems popular - I think it's a bit under-powered for the size personally
"some of the best base-level info to remember can be found in Jim's sigfile" @Lugia
Utility modules are the dull polish that makes the shiny modules actually shine!!!
sound sources < sound modifiers < modulation sources < utilities