might be an idea to lay it out like a rackbrute then, no?
it is very easy to change the number and size of rows and the hp! and with the power module
so it's easy to see how much space is actually available - 8hp??
by the sound of it the first thing you might want to buy is another case
and then a lot of basic utility modules - currently the case looks like an advert for a selection of the 10 most popular modules - workout what you can do with things like sequential switches, kinks -brilliant module, matrix mixers, attenuators etc - remember utilities are for modulation as well as audio - I would go for simpler cheaper functional building blocks over flashier more expensive ones - they generally provide much more flexibility - possibly at the cost of a few hp
of the modules that you mention I would definitely pick up maths though - it's a great module - a veritable patch-programmable analog computer - see the illustrated manual on line for more information
"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