Speaker cable suggestions

My newly put together system is Plinius 8200 mkII integrated driving Joseph Audio RM22si signature speakers (Full system viewable under my virtual system). Current speaker cable is 6' Kimber 4TC biwired (two completely separate runs).

Problem is, current cable is too short for my setup. I need at least 8', and want 10' or 12' to have some slack just in case. Two questions:

1. Plinius has two separate sets of binding posts for use with biwiring. I like the idea of two separate cable runs, versus those that are joined together at 2 leads at the amp end. Is this just in my head, or is it true I will get better sound from two isolated cable pairs, each with their own dedicated binding post?

2. Can you recommend a cable for my setup. I would like to do this on the cheap (<$200 used), but will consider a little more if people feel a huge improvement to my system can be had.

Thanks,
Matt.