Need some treble

Get hearing aids and put it on a setting called HIFI

What I like beyond the inevitable is it how it makes me back up a few years. Decades even. Just enjoy...

Better audio cables or loudspeakers.

I use a Schiit Loki Max and can't recommend it enough...tweak recordings from your listening chair with its remote, and it works with any system as it's analog adding no detectable noise of its own. 

The B135 has pre-out and main-in jacks. Buy an equalizer. The Schiit ones are good, but a vintage 10 or 12 band in good working order is better. Audio Control, ADC, Soundcraftsman, Pioneer, etc.  Check your local repair shop. Or contact Vince at audioproz.com. His used gear selection is excellent and all tested.