I 4th the recommedation of thecableco/usedcable.com. Their lending library allows you to "rent" cables for audition.
As far as silver vs copper... don't buy anything silver clad. IME is causes grunge in the upper frequencies. I have never heard solid silver cables, but have been told by several high end audiophiles that they are a completely different animal.
Also keep in mind that cable design and materials can affect sound... even within the same brand... by affecting the phase/timing of the signal.
This is true from the source to the speakers. Sometimes it might even require changing speaker placement slightly.
I can cheat in this respect because I am using a 7 channel HT pre, (my apologies to the purists), and can lie to it about speaker distances.
My first serious foray into audio was in the late 90's with a high end mid-fi Onkyo HTR... and I used the cables in the box... and lamp cord for speakers. Later I upgraded to Blue Jeans Cables for ic's... and Monster for speakers.
However... when I went to separates... I noticed that the Blue Jeans ic's created a dry notch in the upper mids/lower highs, and a bloom in the lower mids and bass.
Since then I have moved on to the lower end of Analysis Plus ic's... and speaker cables... and I am satisfied. Neutral, detailed, and open.
While the Onkyo is retired... I still consider my system, (higher end), mid -fi... because most of the components are older model used pieces such as B&k, Adcom, Technics... with newer Anthem and Oppo in the mix.
Power cables have also gone from what was in the box... To a combination of the old Tributaries silver series, (series 9, not actually silver plated), PS audio, Wireworld, and Audioquest.
To the OP. Audio nirvana is a journey. Trust your ears when it comes to YOUR system... and give your ears some time to adjust to any cable swaps you make. What you hear initially may sound good or bad... but over time you may notice differences that weren't evident in the beginning. And again... don't forget the possibility of phase/timing issues, and speaker placement adjustment.
Happy listening !!!