I would ask which of the products, if any, came with an adequate cord. Are any of the ones you have closest to the mark? Maybe some are in greater need of an upgrade than others? Or are you asking: Assuming the same fair but not great cord for each, which upgrade would have the most marginal benefit (i.e., bang for the buck)?
Slightly off topic, but I have purchased about 8-10 cords over the past 3-4 years. I have found almost no correlation between cost and quality (however subjectively determined). For example, there is a great cord from a company called Tube Audio Design which sells a great and usable cord for $30 (discounted heavily). I have paid $350 for a "better" brand and not liked it much. Very hard to quantify.
PS I've no affiliation with the co. referenced. Only contact was buying the item with my PayPal acct.
