Need Copper Cables for 18ft Runs: Bang for Buck

My Def Tech speakers are 18 ft from my amp. (Plinius) Looking for bass and high end extension. Can you recommend a solid performing cable top to bottom for a full range speaker in longer runs?I know longer runs degrade the signal more. I need something built to minimize signal degradation caused by longer runs. I'm not willing to spend thousands on the usual suspects for my 18ft. runs like (Cardas, JPS, Wireworld, MIT, Synergistics, Acoustic Zen, Nordost etc.) so best bang for your buck types are what I seek opinions on. I've used Tara Labs Omni, SignalCable, AP Oval 9, and right now Anticables which roll the highs and upper mids. So you can see I've been trying inexpensive brands. I've read some good things about these less expensive brands: MAS, Element, LAT, Reality Cables, Blue Jeans, Oritek,and others. Any thoughts? I'm leaning towards trying out Element: Anyone know the difference between the sonics of their EC double run vs. Twisted Pair? Element says their EC Double Run is designed for larger speakers needing more current and used in longer runs -so they sound like a good choice for my purpose. I'm also looking for a cable that fills in the sound of leaner speakers with out rolling off the highs. I guess I don't want much for my buck! Thanks for your help!