If you want an extremely outspoken declaration of love for the Manley Neo-Classic, see Arthur Salvatore's website, http://www.high-endaudio.com/ He is the crazy Canadian guy whose views seem to be based upon having heard a grand total of four systems, and who gets into cat fights with the editors of Stereophile and the Absolute Sound (why they engage him is beyond me).
You have to be careful to source Electro-Harmonix tubes from a reputable seller with proper testing equipment, as quality control could be better - the ones that are well built work fine and sound okay, while those that aren't can die quickly and tend to hum.
You should indicate whether you primarily seek a push/pull amp or a single-ended amp, as they are of course two very different beasts. There are hundreds of SET amps that use 300B's for output tubes that vary in price from $500 to $50,000 - I don't know where to begin to start with a recommendation except to say that really heavy, expensive ones are generally really heavy and expensive because they have big power supplies and top-notch output transformers (which are heavy and costly). As for lower powered push/pull, the VAC Renaissance 30/30 is superb from the perspective of build and sound quality, and for higher powered push/pull, the same can be said of the VAC Renaissance 70/70. The "Mk. III" and Signature versions of those amps autobias the tubes and have a "sentry circuit" that shuts down any output tube pair that goes out of spec - these features take the hassle and risk out of owning a tube amp (the risk and hassle of finding good tubes to run with a given amp remains).