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

I agree with helomech regarding potentiometers being the weak link in many preamps.  I’m amazed when rather expensive and otherwise well conceived preamps are invariably described as having a “high-quality Japanese blue velvet potentiometer”.  One is a $12,900 preamp from a manufacturer mentioned above that uses a $30 part to perform arguably one of the most critical functions.  Many times they will not make it obvious what part they are using and you have to look for pictures under the hood.  I move right along whenever I see a potentiometer.  

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.