Recommend The Best No Frills Preamp up to $5K.

Aric Audio preamps. The Super 6Sn7 is excellent at $4,625, the Motherlode II is brilliant at $5,750 as long as you don't need XLR connections, and the Motherlode XL at $6,875 is one of the 2 finest preamps I've ever heard.....magical, pulled my entire system up another level.

Don Sachs/Lynn Olson Raven preamp at $6,395 (sold by Spatial Audio Labs)  is the only preamp I know of that comes close to the Aric's Motherlode XL.....brilliant

When you say "no frills" that could mean a lot of different things. But my brain immediately goes to an unusual option in the Pass Labs HPA-1. It's marketed as a reference caliber headphone amplifier but also works as a simple preamp. By simple I mean just 2 RCA inputs and 1 RCA output, manual volume control using that big beautiful Pass knob, no remote control.

I know a few people using it and they say it punches way above its price. It's also a great value since it originally sold for under $5k and can be had used for as low as $2k. This assumes you can get by with the simple functionality. You do get the bonus state of the art headphone amplifier though.

There's a new version called HPA-1c which has some mild refinements. Still within your price range but I feel the original is a steal on the 2nd hand market. It's a Pass so basically indestructible anyway.

BAT VK-80.   There's one for sale right now at your price point here on A'Gon.