What process do you use to purchase cables?

Adding to what @jond said. It takes a long time to fully appreciate the effect that a set of interconnects produces. So, after lots of research I almost always need to live with a couple different ones for weeks. I usually end up buying a couple different pair. Although my dealer has let me keep a couples sets of Cardas Clear Beyond for a couple months while I compared with a couple sets of Transparent I own. Right now the Transparent win on components and I am still unsure on the amp. 

Unless you are planning to purchase your components from the used market and you are truly looking for a place to start your cable search, consider the advice of your dealer. He can tell you which cables will work well with what you are buying and for what you are trying to achieve. Personally I have had the best results by staying within the same name brand for interconnects and speaker cables. I use a different brand of power cords but they too are all of the SAME brand. If you are going to buy used or not through a dealer, pick your components first. Then either ask for forum advice based on what you have or try one of the cable lenders mentioned. Good luck!

I think you're past process is a solid way to go.  Personally, do not feel cables make a significant difference (fighting words I know).  Of course, buy quality cables but feel speakers, electronics, and room is where to focus the money.  Just my opinion.

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When looking for a new IC or speaker cable, I read the manufactures web site data.  If they have 5 to 10 levels of cable, be wary.  Most cable companies offer a 15 to 30 money back trial, shipping on the buyer.  2nd step is to see what the Agon or ebay etc have used from the company.  I choose the ones that aren't sold second hand for the most part.  Zu speaker cables and Audio Envy are very hard to find in the used market.  When I get the new cable, replace one and leave my original in place.  Zu and Audio Envy never go back.  My Morrow Audio ICs are currently being replaced.