Dell HP-P2507F3P
enough said. 😉
... or anything with a *P2507F** in the model number. HiPro is the parent company / manufacturer of these, and one of the highest-quality OEMs, IMO. So these PSUs may also be branded as their own (HiPro) or as Chicony. I think HP also used these for some of their systems at the time (mid 2000's.)
These PSUs are basically tanks. They offer a very balanced 5V/12V group regulation, making them suitable for both old 5V-heavy systems and newer 12V-based systems (they often came with Pentium 4 Dell systems from 2003-2006.) Typical output wire arrangement is a std. 20-pin ATX connector, 4 or 5x molex drive connectors, and one or two floppy connectors... so good enough for most retro builds. Only slight downside is the lack of a -5V rail, which shouldn't be a huge deal, except for some very specific ISA cards that actually need it.
The reason I like this PSU and other similar models from HiPro is because they have a lot of space for the output filter caps inside - most caps are 12.5 mm in diameter. So when recapping, it's really easy to source caps for these PSUs. Also, while recapping these PSUs is recommended, I find a good deal of them are still perfectly usable with the original caps. My general rule is, if I see one bulging cap in these, I recap them. But if I don't, then frequently I use them as-is. They are so over-built that usually a bulging cap or two will not make them produce excess ripple & noise in most cases - though at that point, a recap should be planned, as one bulged cap means the other ones are probably also close to EOL or already there but not showing it yet.
This specific PSU aside, I also like the newer HiPros too. Namely, HP-P3017F3... though these are from the late 2000's and usually come with 4x SATA power connectors instead of 4 molex. So they are not as retro-friendly "out-of-the-box" without adapters. But other than that, they too have a pretty solid 5V rail and excellent cross-loading performance.
Alternatives from other manufacturers like Delta, LiteON, and Bestec are also good.
Be extremely *careful* with Bestec, though. The one model of theirs to AVOID is the ATX-250-12E - it's a known motherboard killer *when* (not if) its 5VSB circuit fails.
The nearly-similarly named model, ATX-250-12Z is built differently and completely fine, though.
Delta also had some designs similar to the problematic Bestec mentioned above, but somehow they just didn't seem to fail as catastrophically... and not as often either. No specific model numbers of these, as most are always in the form of DPS-xxxyy, where xxx is a number usually the same as the max rating of the PSU (e.g. DPS-300yy = 300 Watt PSU model, and DPS-250yy = 250 Watt) and "yy" is a 2-letter code that is more specific to different PSU models (e.g. DPS-300AB and DPS-300KB are very different PSUs in terms of layout inside and also some parts of the design.)
