I've an old Phonic- branded 12 track mixer.
It has plenty of gain without a DI box in front of it. Turn the gain up and it even distorts quite acceptably. It drives headphones with ease and the onboard EQ is pretty good, too. I use one of the in unused to run a tuner, and mix in a "music source" via a 3.5 stereo jack to 2 phono cable. The mixer has phono sockets for the last pair if stereo channels.
Playing through headphones can be a bit of a culture shock. Lots of string noise, and undamped strings ringing. These are good t things. Teaches you to eliminate them from your playing. A good pair of headphones will easily cover the entire frequency range that a bass can produce, but it does lack the physical element of the lower frequencies that amps & cabs generate.
Think it cost me £80. Has no onboard effects that some do. Another bonus; the first 4 channels have gain controls and XLR inputs. It's possible to configure each channel for a different bass and just plug into that depending upon what instrument you're using. It also allows the use of stereo effects and also instruments with more than one output; Rickenbackers, Yamaha Attitudes, Chapman Sticks, anything driving synths with midi, or even just a wet/dry mix from a pedal that has a clean output but no control of its own.