300b vs 845

Another manufacturer making both is Viva from Italy, I use the 845 SET integrated, the Solista. I have heard 300B and I would agree with others opinions, that it may have more "midrange magic", but I feel the 845 is "truer", more accurate across the range and more neutral. I personally love the 845 and would'nt change, but my word, it does run hot. How the Italians manage with their Summers, I have no idea. I am seriously considering a SS integrated for Summer use, perhaps the Lavardin.
In truth, I don't think you can go wrong with either and you won't be rushing back to transistors.

I concur, thanks to Phil for an excellent summary of his vastly greater valve experience than mine. i have just as it happens, installed the 845B valves in my Solista and am very impressed. I don't know if I would describe it as darker, but the base was the first thing I noticed. The amp audibly goes deeper and I believe the treble is better defined too and with better imaging too. i am tempted by the 845M valves, but I'm told they shine like searchlights and my wife is already muttering darkly about the heat from the Solista. I think anyone taking the plunge needs to take the greater heat with 845 based amps, into consideration, it really makes Summer use problematic.
Excuse me if I bang on about the Viva amps, but they are not as well known as they deserve to be. I believe a review by Art Dudley in Stereophile is imminent.

Regarding the use of 845B's with a Viva amp. The ones I used on my viva Solista glowed a most attractive cherry red colour before they quite rapidly failed. Presumably the voltage on the Viva is a tad too high.