Here is my build:
Silverston Technology Grandia HTPC Case - Silverstone cases are the dog's whatsits by the way, I wouldn't use any other brand
Intel i5-3570 quad-core 3.4 GHz CPU
Asus P8B75-m/CSM motherboard
16 gigabyes of DDR3 RAM
EVGA GeForce GTX950 2 GB gaming graphics card - I think you need at least a 950 series to get 7.1 playback
Samsung 850 Evo 120GB SSD for software
Mediasonic ProRAID 4-bay RAID10 enclosure with 4 x 3 terabyte "spinning rust" hard disks (WD Caviar greens I think), giving 6 terabytes of RAID10 storage
OS is Windows 10.
All of this plays back in 4K via an Audioquest Chocolate (yes an expensive cable, get used to it) HDMI cable to a Marantz SR-7010 receiver to a Samsung 6-series 60 inch 4K TV. My 19 ft x 12 ft home theater (sic) room is set up for 7.2.4 surround sound using Yamaha's excellent value for money "Natural Sound" range of in-wall and in-ceiling speakers, 50 W RMS, 150 W peak each one. I'm using cheap Polk 10-inch subs at the moment, but expect to upgrade these to 12 or 15 inch units in the new year. I have an extra pair of speakers that the builders put in left in the ceiling half-way down the room but I can't be ahem'd to take them out and fix the holes left in the ceiling, so I have the capability for 7.2.six, and the room is wired for up to four subs. Overkill? Yup. Future proofed? Unless "in floor" surround sound is the next latest and greatest, you bet!. A 4K PJ and screen are on the list, right after I convince the wife to sell her kids for medical experimentation.
I use AnyDVD-HD and MakeMKV to rip all my DVDs and BDs to MKV files. You can probably get by with just MakeMKV for most discs, however, and AnyDVD-HD seriously slows down the ripping time. Using MakeMKV you also have the option to "back up" your discs meaning they'll play back like discs in a player, but I just rip the main movie files and leave out all the "special features" and other padding to save on hard disc space. I actually do most of my ripping on my home office i7 hex-core PC because it's faster, then transfer the files over our home wired network.
Playback is handled via Cyberlink PowerDVD version 15, although I think version 16 is the latest.
So long as you select the right audio files in MakeMKV you can get up to 7.1 playback, which is enough for all DVDs and all non Atmos BDs.
A DVD takes up between 3 and 3.5 gigabytes. A Blu-Ray around 30 gigabytes. I am told, though have no experieince, that a UHD BD will take up around 60. On my 6 terabyes I have ripped 300+ DVDs and 100+ BDs and have enought room for about 20 more BDs. When I hit that buffer I shall add another RAID10 unit, same enclosure but with the latest "spinning rust" models and if prices come down, using 4 or 6 terabyte drives to give me 8 or 12 terabytes of storage. One more unit should see me through to the eating only soup and pre-chewed food, soiling own Depends, stage in life.
Since I mainly used the HTPC for ripping the old collection of non-Atmos DVDs and BDs, enabling five crates of DVDs, BDs and CDs to be put in the attic out of the way, I wasn't concerned about Atmos.
And I did all this myself, including re-wiring the speakers through the walls and ceiling with 12-gauge speaker cable.