in the context of this thread? Difficult, there's a lot of choice and it really is a question of finding the right match. Puresounds 'bewitch' is a good amplifier, praised a lot and looks good but its price seems a little bit steep considering how much they are 'china direct', even considering postage and the tweaks the uk importer has specified. Still, for warranty purposes and the improvements made its not really a clever option imo to import so the price is roughly in line with other products here. Prima Luna, Melody, Icon etc all make well reviewed products, some a bit more costly than the budget here, others within. A crossover product such as one of Unison Research's hybrid integrated amplifiers may also be a good option, especially if higher power is important.
My experience with valve amplifiers other than very brief listening to the recent A30 and a melody integrated is with older products so I can't be specific, sorry.