Ok , i can see where his response could have been worded better, but i wasnt trying to critisize or belittle you in any way. more so commenting on the fact of choosing fish that you like. getting input from others is always a great idea. researching fish of interest is always the responsible thing to do. But im sure you know that even if everyone is saying to get fish A or B that untill you try it for yourself, you may never know and even have different opinion once you do.
As for an umbee in a 75 or 150, well if you get them small a 75 is fine to growout and even keep a pair up to 9-10" as long as there isnt any aggression. a 150 is good too for a few years. once Umbees and dovii's hit 12" their growth slows down compared to the first year. so depending on your feeding cycle and growth of your fish would determine how long you keep them in either tank.
Gage is the vendor on cichlidconnection

the other site you asked about is snooken aka John. ive heard great things about him. Grammode do grow slower than anything on your list, even slower than festae. if you do want grammode try hitting up Dan aka cichlvr he has 4-5" pairs on his list. at least they are already paired up and saves you the time and effort. plus theyre not expensive

Good luck. If you decide to get umbees then hit me up bro