by 10 x 84hp do you mean 10u or 30u?
if 10u:
it's not really a much bigger case than the one you already have... only 60hp more for 3u modules + a 1u row
is this in addition to the 6u 104hp case you already have or a replacement? as an addition it's fine - although I'd probably go for a 104hp case so they can be arranged better and not be ciffering widths, if it's a replacement, then there's not a lot of extra space to grow into - so the next case will be wanted/needed sooner rather than later
if 30u:
I really wouldn't want a monolithic 30u x 84hp rack...
I'd go wider and lower - I have, effectively, 18u * 188hp - made up of 4 cases (2 * 9u 104hp, 2 * 9u 84hp) so that the lower 2 are near horizontal and the upper 2 are near vertical... this is much easier to deal with than 30u straight up imo - so I'd halve it vertically and double the width to give 15u 168hp - it's also better for module arrangement - I kind of follow the arp 2600 layout & that works quite well
"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