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.