First look: Basic black. Pretty in black and a pig to keep clean. Every touch leaves a finger print. Perfect for a mid size quiet machine.
I will post port information and pictures when I build a computer using the case.
You want small but not cramped size and USB 3.
The width of most cases is determined by the width of a DVD drive. The power supply and other items are designed to match. There is very little variation in width among tow cases.
The front to back length, or depth as the Americans like to call it, is determined by the length of add-in expansion boards including massive graphics cards. Most cases are similar. Some disks at the front then the expansion cards. The Solo II has a gap under the disks for a small number of very long cards. The original Antec Sonata cases accepted more disks and had room for every expansion card I tried. The Solo II accepts one less disk, one less DVD drive, and two incredibly long expansion cards with a length that I have never required on any computer.
The height, at 440 millimetres (17.3 inches), is slightly less than the current Sonata cases and almost exactly the same as the original Sonata case. That reduced height is useful if you are building anything that is not a storage server. Something higher could be useful when you require eight disks in the one case.
You want USB 3. Your next motherboard will have two USB 3 ports at the back. You want some at the front of the case. The Antec Solo II has two USB 3 ports at the front of the case and they connect to the motherboard using a 19 pin USB 3 header connector.
Your next motherboard will have a USB 3 header socket. If your motherboard does not have the socket, you have the wrong motherboard. The 19 pin socket might be called a 20 pin socket because it is a 20 pin socket with one pin blanked out to stop you inserting the plug the wrong way around. The socket also has a slot on one side that matches to a ridge on one side of the plug and should stop insertion accidents.
The 19 pin connection handles two USB 3 ports. You can use one port to backup your disks while using the other to import many big images from a modern fast USB stick.
The old Antec quiet cases, the Sonata series, had the front USB ports under a flip up cover and they still ended up covered in lint because there was some air flow around the sockets. The Solo II sockets look like they have sufficient seal to stop the air flow.
The Antec Solo II is perfect for two disks (not counting your SSD) with the absolute minimum of sound or three disks with a slight increase.
Antec have several quiet Sonata cases from the similarly sized Sonata Proto up to larger units for more disks but not really the size you would use for a storage server. The larger Sonata cases will fit four or five disks in a minimal RAID 5 array. Antec have some other case models for more disks but not the same level of quiet.
The Fractal Design Define R3 offers 8 disks in a case only 251 millimetres (20.5 inches) high and a similar level of noise reduction. There are several reasons I would not use the R3 for a workstation, including the stupid USB sockets facing up instead of out. If I needed five to eight disks in the one case, the R3 would be on the short list for consideration.
There are other brands of cases with quieter than average cases but not really quiet cases. In many cases the fans make the most noise and a below-average-noise case can be made into a genuine quiet-case by replacing all the fans. If your case is supplied with a power supply, replacing the power supply with a quiet power supply might be expensive.