I really don't need it to provide all that much power--I'm sure 300W would be more than sufficient for the machine. The reason I pointed out the Cooler Master is because it was cheap, from a brand I generally like, and had the flexibility of 20+4 and 4+4 connectors. I'm certainly very open to other suggestions though.
I would very much like to get a modern PSU for this that can handle the older hardware, though, as it's not all that unlikely that one day I'll need to replace the MB and CPU with modern components anyway.
If you could recommend a cheap but reliable PSU (it can be low wattage, like I said I'm sure 300 is more than enough) that can power both ATX and ATX12V decently, has independent voltage regulation, and preferably has a 20+4 MB (this board requires 24, but I like the flexibility) and 4+4 CPU (this board requires 4, but again, I like my options open), I would be grateful. Apologies if I've been difficult to help.
EDIT: A couple SATA power connectors would be nice as well, but I'm 99% certain this rig would never need any PCI-E connectors. Thought I should toss that out there also.