My prediction is this - next year you'll need a bigger box as you will be buying more stuff you think you need. Been there , done that. And your on a tool collector site. It's like AA here. More like TA. Someone needs to make up a 12 step book to help us out.
I like small stuff, so unless I can find a kra65 at a price I can afford then I don't imagine myself needing anything else for a stand-alone 1/4 set like this.
It is definitely a slippery slope between this box for my main set to upgrading to a kra65 and using this box for a secondary 1/4 set.
Just thinking about what my main 1/4 set was before getting the Mac mc1 and this current set is a big step up, so you're not exactly crazy.
I've got this thing pretty packed, but I know if I get something else just to give the tools a little more " elbow room " I'd just pack that set.