I'm surprised no one's mentioned the Linear Tube Audio MZ2, a very fine little 6SN7 based preamp with separate linear power supply. I got a Freya, and was quite happy with it, until I tried the LTA, and have not gone back (Freya for sale). And that is before doing any tube rolling, which I look forward to. BTW, well below your budget.
Don ivey
Don ivey