+1 ^^^^^^^^^^^^^^^^^
Given the price limit specified and the preference for valves, you might try the Schiitt Freya + preamp. It is selectable between a passive setting, zero gain, a "buffered" solid state stage and a tube stage (octal, 4 tubes) with 12dB gain. It is well-reviewed and reasonably-priced. Schiit has a direct sales distribution but their warranty service is good.