Lots and lots of solid recommendations here. I don’t disagree with any of them.
However, I suggest you take your browser to the top the "amps-preamps" section and click on the "Popular all-time" tab. At the very top of that tab you’ll find the "Preamp deal of the century" thread. Over 26 million page views. It spans two decades. It is all about Supratek preamps, hand made in Australia. The "entry-level" Supratek preamp is well within your budget. These are very highly regarded preamps. Hand built. Point-to-point wiring. LIFETIME GUARANTEE.
Oh, one more thing. There are a few posts on this thread that are critical of the 6SN7 tube as being "iffy" in quality and reliability. I respectfully disagree. The Suprateks are supplied with readily available tubes that are very reliable and last, like, forever. There are a lot of good 6SN7 tubes out there and there's a reason they're used a lot in preamps. They sound great. And there are good ones currently in production. Psvane, Linlai, for instance.