Those are pricey, i will need to see about precisionresistor.com as well.
I'm *know* that "Econistors" have an excellent track record over many years of use in military, aerospace, and automotive circuitry. The resistors from Precision Resistor *may* be just as good [or even better!], but I have no historical information about them, and so I am hesitant to use them... If anyone has long experience successfully using their products, please post about your experiences here!
I have purchased three of their MC-7 kits, one standard and two with values of 2.5 and 5. They were extremely helpful and quoted me accurate lead times of 10 weeks for the two non-standard sets. I also had them make a 10M 2.5W resistor that rounded out my original MC-7 kit. The prices were not cheap, but the kits were made using 1W non-inductively wire wound parts. I used them since I frequently travel near their business.
If you price out similar resistors, you will find that the 1W 5ppm resistors can cost much more. I have not priced smaller wattage units, but you can expect a quick reply from them if you send them your specs. I would imagine that the pricing would be competitive to what you will find elsewhere.
I do not have the capability to accurately verify the tempco but they measure well within tolerance on my 3458A. The quality seems to be excellent but I do not have much historical information on their performance.