Dell XPS 8950 with RTX 3080 and i7-12700
Looking over Memorial Day Sale discounted computers, I decided a Dell XPS 8950 configured with a RTX 3080 GPU and i7-12700 CPU had the grunt to drive my new Valve Index VR headset at a price I'm willing to pay. My next stop was the XPS 8950 service manual. Flipping through component replacement procedures let me get a look at the design for this system. I liked seeing its clever layout and tool-less operation. I especially liked the brace that help support video card weight. GPUs been growing bigger and heavier and I've been grumpy the industry has not yet coalesced on a de-facto standard to support all that mass. For the most part they're still just mounted on the backplate and cantilevered way out past the PCI Express slot, placing a great deal of strain. Motherboard manufacturers have started putting metal reinforcements on their PCI Express slot, which I consider a hack and not a solution, but that's an entirely separate rant so I'll stop here.
The downside of novel capabilities is a nonstandard form factor. Historically, by the time I want to upgrade a CPU/motherboard combo I'm ready for a new system anyway. (Like right now.) Therefore, I'm not terribly bothered by the fact neither the mainboard nor case are standard ATX: they're tailored specifically to each other. There's an upside, though. Front panel ports here are actually mounted directly on the mainboard and not connected via cables as is typical of a standard ATX case. I've had intermittent connection issues with such front panel ports, so I see this design as a positive.
The only part that made me pause was the proprietary power supply. Unlike CPU/mainboard combos, I have had to replace power supplies on my own PCs. Mitigating this worry is (1) XPS power supply should last longer than lowest-bidder ATX PSU, and (2) power plug could (might?) be compatible with the new ATX12VO standard. So I could rig up something to keep the machine running, even if it wouldn't fit in the case properly.
That was enough information for me to decide on buying one. One thing the manual couldn't definitively show are the cables, so I had to wait until my system showed up to see them. They are laid out very tidily as expected of a customized power supply with all wires trimmed to necessary length. It is also free of all legacy power plugs. No floppy connector, no CD-ROM connector. Lack of clutter ensures great airflow through the airy middle section of the case.

I was happy to see robust provision for GPU power. There are a pair of 8-pin PCIe power plugs to feed the existing RTX 3080 card. Waiting in the wings just below them, tucked into a plastic bracket, are a duplicate set of extra PCIe power plugs. Together they are enough to feed a RTX 4090 card and I feel comfortable they are ready for whatever video card I might want to upgrade to in the future.
Only a single PCIe x1 slot is still open for future expansion, but historically that has been sufficient. This system came with 32GB of DDR5 RAM in two 16GB modules, leaving two additional memory slots open. There are two M.2 slots, one of which is occupied by a terabyte Samsung NVMe SSD and the other open. If I want to add some bulk HDD storage, there are two unoccupied 3.5" drive bays. Both of which have SATA power plugs ready to go. However, only one of the two bays have a SATA data cable and the proprietary tool-less drive caddy installed. (Look for blue plastic in upper-right corner of picture.) SATA cables are easy to get and there are open SATA ports on the mainboard. It might not be as tidy since the length isn't customized for the case, but I'm not worried about that. I'm considering buying one caddy now. It's pretty cheap, and ensures the bay is usable even if Dell stops carrying this part. Or I could measure the dimensions of my existing caddy and 3D print a clone.
I saw no open 2.5" drive bays, but that is a solvable problem. This system came with a laptop-sized DVD-R/W optical drive that I do not expect to ever use. However, that gives me the option to swap it out with a 2.5" drive adapter. I'll just have to remember to get the correct height adapter this time.
With the exception of power supply, I see standardized form factors for everything else I anticipate installing as either replacements or upgrades. The non-standardized elements have offset benefits like GPU support, tidy cabling, good airflow, etc. This compact integrated package seems well worth a ~15% premium over a DIY build. Now I have to see if it stands up to the test of time. I hope this machine will support many adventures (VR and otherwise) for years to come. Starting with revisiting my favorites to feel its upgraded power.