There are certain compromises that come with building a compact PC, but power does not have to be one of them. Proving so, Silverstone's new SX1000 dishes up 1,000W of power in a package that fits into smaller cases that don't have enough room for a full-size ATX PSU. The end result is a PSU with more than enough juice to feed even the most power hungry gaming components.
The SX1000 adheres to what Silverstone calls the SFX-L form factor, a term it created. Standard SFX units measure 125mm (W) x 63.5mm (H) x 100mm (D), whereas SFX-L units are a little longer. In this case, the SX1000 has a depth of 130mm. Regardless of the form factor, it's good practice to check the supported dimensions of your case when purchasing a PSU, particularly compact cases built for micro-ATX and/or mini-ITX motherboards.
Silverstone actually announced the SX1000 last year, but there was no mention of a price or release date. Now there is a retail listing at Amazon in the UK. There's still no mention of a price (it shows as being temporarily out of stock, because what isn't these days?), but actual retail availability is rarely far behind once new items receive retail landing pages.
Your next upgrade
On paper, the SX1000 would be an impressive PSU even if it didn't ship in a smaller size. In addition to being a 1,000W model, it is 80 Plus Platinum certified, which denotes a high level of efficiency (basically meaning less power gets wasted as heat). The other higher 80 Plus rating is Titanium, and those are comparatively few and far between.
This is a fully modular unit too, which has increased importance when putting together a compact PC. Connectors include a single 20+4 pin, one 4+4 pin CPU, two 6+2 pin PCIe, four SATA, three 4-pin peripheral (Molex), and a single 4-pin floppy. That's everything you need to feed a decked out gaming PC. The green team introduced a 12-pin connector with its Nvidia RTX 3090 and other Founders Edition cards, but those come with an adapter in the box anyway.
As for the mystery of pricing, my best guess is this SX1000 will check in at around $300, maybe more. Serving as a point of reference, Silverstone's 800W model with 80 Plus Titanium certification runs about $214, so there's your jumping off point.