Regular readers will know I'm fond of tiny computers. During my search for one powerful enough to play games on, I found several beautiful and well-made options. But none were so wee as the Zotac Zbox EN1070K [Amazon], which is roughly the size of a Sega Dreamcast. I've had it for six months, now, and can report that it's great: easily the most enjoyable, compact, no-nonsense game-ready PC I've ever owned.
Miniaturization is accomplished by using the MXM video card form factor originally devised for laptops. In the past, this would have resulted in a severe performance compromise. But current Nvidia models hit close to the numbers posted by full-size counterparts. Even with Zotac slightly underclocking the GTX 1070 (presumably for heat reasons), it benchmarks close enough to the full-size model that I doubt I could tell the difference side-by-side.
There's even a model with the GTX 1080 [Amazon] in it, but it's twice the size of this one and I wanted small, and it turns out the 1070 is more than enough for every game I've tried, outpacing the GTX 970-equipped PC I upgraded from. The latest games on the highest settings on 4k monitors would be pushing it, I'm sure, but if you need that, maybe a PC the size of a hardback novel isn't in your future.
There are compromises to bear in mind. Upgrading the i5 Kaby Lake CPU is possible, but I won't be chancing it for a long time -- it voids the warranty and requires almost complete disassembly. The MXM video card is easier to replace, but such things are not really consumer items and you'll have to pay outrageous money for something ripped out of a dead laptop to beat what's already in there. The ZBox isn't a console, but upgrading the gamey bits would be hard and expensive work.
And beware the EN1070 (without the K) -- it's the 2016 model, with a significantly slower CPU and not much saved off the price. (The new ZBoz Q workstations use the same case too, by the looks of it)
Upgrades to RAM and SSD (there's both an mSATA header and an M.2 slot) are very easy, though. With 32GB of RAM and a 512GB Samsung 960 Pro installed, this is an astonishingly powerful little box and I'm very happy with it. The price premium of smallness isn't terrible, but it is significant: about $250 over the cost of a similarly equipped Mini-ITX PC specced out with equivalent gadgetry within.
The only annoyance, for me, is the case design. You'd think it'd be the sleekest most minimalist thing going, but it looks like an off-brand cable modem, right down to the plastic fins and haphazard port placements. There's no annoying gamer greebling or red-LED edgyiness, thankfully. It's well-engineered, too, easy to open up and add memory and storage. It comes with a fairly large power brick... but not XBox One large.
I'm tempted to pad this out with benchmark charts, but the proposition here is simple enough, so there's no point bothering. If you want a genuinely powerful and tiny game-ready PC and you don't plan on frequent upgrades, just get this one.
It's about $1130, and you'll have to bring your own RAM and storage. The bundled options on Amazon are a poor deal: get it barebones.
Zotac Zbox EN1070K [Amazon]
210mm x 203mm x 62.2mm Intel Core i5-7500T (quad-core, 2.7 GHz, up to 3.3 GHz) 2 x DDR4-2400/2133 SODIMM Slots (up to 32GB) GeForce® GTX 1070 8GB GDDR5 256-bit 2 x HDMI 2.0 2 x DisplayPort 1.3 1 x 2.5-inch SATA 6.0 Gbps HDD/SSD bay 1 x M.2 PCIEx4 / SATA SSD slot (22/42,22/60,22/80) SD/SDHC/SDXC card reader Microphone, Headphone 2 x USB 3.0 1 x USB 3.1 Type-C 1 x USB 3.1 2x USB 2.0 Dual Gigabit LAN 1 x WiFI SMA connetor 802.11ac/b/g/n
P.S. Here's the back: