Mouser or Digi-Key?
Like everyone else says, use big-name vendors only. At this point I'd say no to Jameco, I've had fake IC issues with them.
Nichicon and Panasonic
Also Rubycon, Wurth, and CDE/Illinois Capacitor. We do tend to only order Nichicon for low ESR.
Unfortunatley axials are getting hard to find, so I often sub in radial for axials so I can get high quality.
CDE/Illinois Capacitor still produces a lot of the Mallory part #s for axial, that's 99% of what we order for axial. The rest are Vishay (well, really, other companies Vishay has absorbed!). Sprague still makes caps too. On X/Y safety caps, I actively avoid Kemet nowadays. They seem to have purchased RIFA and make caps that look *exactly* like original RIFAs. For the larger values I use poly caps usually from WIMA. For small values, say 2200 pF and less, I use ceramic X/Y dual rated caps as they're smaller than the originals and means stocking one thing only. Thanks, Jonathan