a better interconnect cable

I strongly encourage you to check out Hapa Audio with their Ember RCA cables fitted with KLE Absolute connectors. To say their new design is phenomenal would be a complete understatement. Even in a modest system like mine, the addition of these cables has improved the sound past what I ever thought possible, to the point I even postponed some bigger gear updates because I didn’t feel the need to upgrade. With a lot of other rca cables I have tried, I bounced between smooth but dark/veiled sound or detailed but thin/tinny/clinical sound. None have been so smooth and palpable sound while still maintaining that vivid, airy soundstage. And hearing the inner detail buried down in the music come to life for the first time is incredible. It is like the old adage that an item is perfect not when there is nothing left to add, but when there is nothing left needed to take away. They are by far the best cables I have ever owned. I realize they are under your listed budget, but I know their performance does not match their price. One big perk to buying from a small company.

Hapa Audio

First off, consider what you have and where you would like to go. If you want more bass, go with a cable that has conductor of larger diameter than what you have and if you want more highs go with a cable that has a conductor of smaller diameter. As for details and speed, to get more you need a cable with a lighter dielectric, look for some dielectric that introduce air around the conductors. As a DIY cables enthusiast and micro manufacturer, I make IC cables with 20, 22 and 24 AWG OCC copper, each rendering a slightly different tonal image  with the 20 awg having more bass and the 24 towards the leaner side. For the dielectric, to have a sound as fast as it can be, I use layers of braided natural fibers to enclose and assembles the conductors.

buy OCC single Crystal that's the best wire for audio and has been proven to be the best for over 40 years now.

I too went with self made cables. I used Belden cable and Switchcraft connectors. 

Townshend Fractal F1s are very good and worth an audition