Are you after a dedicated mini-itx case, or a small matx case?
Options in the mini-itx area seem to have stagnated in the last few years (nothing new on the market), the Inwin Chopin and Cougar QBX being the main ones I'm seeing recommended in addition to the Cooler Master NR200 series and the Silverstone SUGOs...
If I had something like this but reliable and with 2 usb ports, I could keep the existing case and just not hook up the existing front usb, which I use. Any good 5.25" drive bay things like this. Searching on amazon I get too many cheap looking ones. I'd like the faster microsd slot reader but it isn't necessary as I have an external one. The ones with esata ports seem interesting too, though I have that as an add-in card already that I use for backups.
The issue I have with cases is that they are meant to be a tower and not meant to be horizontal and have weight on top of them.
I'm a big fan of the Cooler Master NR200, which is a big boy for mITX but it does support at least SOME 3-slot uATX boards by relocating the PSU cage. It's definitely sturdy enough to support real weight on it and can be used in any orientation. It can handle a full size GPU and it has nifty magnetic side panels. Gigabyte even makes a B450 board that supports four DIMMs and fits in that thing.
No external bays on it, though.
I can vouch for the Cooler Master N200 (note the lack of R, this is a microATX tower), I've come across a few in my work and they're solid enough. The metal's a little thin, but it has a nice featureset for a case in its budget segment and it's not super gaudy or flashy. I'm not crazy about them when the Fractal Design Core 1100 exists though -- I've actually used the Fractal for my P4 build, and while it's a little old school (top mounted PSU) and cable management is less than totally elegant in it, I'm very very very impressed by the build quality especially for the price. For less than you can buy an N200 for right now, the Core 1100 is built way, WAY better. If I were to be looking for a case for my main PC right now, say my Phanteks Enthoo Pro spontaneously melted or whatever, this would be what I buy. Especially since I'm using a microATX board right now and have no use for anything that big.
Cooler Master N-whatever or S-whatever are pretty great cases. They've kind of replaced Antec as providers of a generally good if unspectacular chassis. Actual Antec kind of went off the deep end with weird RGB and festishy skeletal styles for everything but the most basic models. IMO the P5 is the last decent Antec chassis.
I'm keeping this case and just buying this: https://www.amazon.com/gp/product/B00UBFXMXG
It will replace all the front ports and seems well reviewed. Problem solved.
I just have to wait for restock of some of these cheap A520M boards.