I have sold Ohms in the past and my current #1 speakers are omnidirectional Mirage OMD-15s, so I'm very familiar with the tonal balance, dispersion pattern, and imaging of omni's like yours. I just put in new speaker cables--the Zu Cable Libtecs, and they are WONDERFUL! They are 11 gauge, yet are a little less than 1/2" in diameter. They use a proprietary winding that retains the phase relationships as evidenced by stronger bass, bigger, fuller soundstage and better imaging. Granted, the list price is $1199/pair, but Zu's promotional dep't puts a few pairs out on eBay with a starting bid of $1 to stir up some word of mouth. The $1200 Libtecs typically go for $250-300 there.
To keep it inexpensive watch eBay for are the Zu Wax speaker cables. They list at $599 but typically auction at $125-150/10' pair on eBay from Zupromos. They are brand new with Zu's normal 60-day trial/return policy.