Extra length is fine and don't let some big box store tell you that they have to be the same length on each speaker either. Electricity travels at nearly the speed of light.
Check out your local Home Depot or equivalent for bulk speaker wire pricing. Then check out Monoprice's 12 guage. I have used both. Both will sound identical but the Monoprice is wayyy easier to work with as the home Depot stuff is annoyingly stiff and kind of ugly, if that matters. BlueJeans and Axiom both get great comments here as well for it's workability.
Don't worry about built in spade clips, you can buy them at your local Radio Shack for pennies a piece and crimp them on with just a pair of pliers. A proper crimper does a cleaner job, but as long as it is good and tight, you are absolutely fine. Throw some shrink wrap over it if you like to keep i t clean looking.
