Buying speaker cables on-line: Is this advisable?

I am in the market to upgrade my speaker cables for my system and will definitely be interested in considering used cables because of cost savings.  I've started doing a considerable amount of research on selecting cables and it's very possible that I will buy the cables on-line.  The dilemma I have is being able to see/hear all of these different cables that I am considering before making a decision.  Are there certain questions I should be asking about performance or construction when making a decision?  I have a solid state amplifier, Ayre AX-5 twenty.  Are there certain types of cables that perform better with solid state amplifiers?  Is there a way of getting performance information from manufactures like MIT, Purist, Kimber, etc?   Is there is any situation in which one could consider purchasing cables without first hearing them in a system.  Any and all thoughts are welcome as I continue this journey.  Many thanks.