I've been doing projects that require some 3/4 extension, epoxy coated slides like the KV 1284 or Blum B230's. I've been buying the Blum's from Woodworkers Hardware. The prices are great, the selection great, etc.
That said - with some forced belt tightening, I continue to look for less expensive slides -- and am willing to give up some quality.
Gliderite.com is often mentioned - but they seem to be out of the 3/4 epoxy styles. I'm not an eBay user at all - just can't get comfortable with the risk/reward ratio.
Doing a google - this company