Celestions seems to be the benchmark, but more expensive than needed. Warehouse Guitar Speakers are very nice replicas/knock offs of the Celestions. Webers are modern takes on vintage speakers, Celestions, JBL's, and Jensons. Webers also tend to be a reasonable deal. Scumbacks, used to be cheap, not really any more, are designed around the Pre Rola Celestion Marshall speakers. More than anything, you have to find out what kind of sound you are after, then you can find the appropriate model and get the brand that fits the cost benefit analysis the best. For comparison, the Alnico's tend to be chimey, the vintage greens tend to be warm and break up easy. Most everything else is in between somewhere.
Patrick