I ran Response 2.5's both ways, and didn't notice any real difference. Just be sure to replace the metal jumper bars with some quality jumper leads. The same brand/model as the speaker wire is of course ideal.
All other things being equal, I think it's more cost-effective to put the $$ you would spend on two runs of wire towards a better grade of single run.
Of course, there are speakers that more or less demand bi-wiring; this isn't one of them.