While i hate to be the bearer of bad news, there are NO speaker cables made that will suit your needs and not result in signal degradation is some form. With that in mind, you need speaker cables that have the following traits:
1) Heavy gauge wire for lowest possible loss
2) Low inductance to maintain even tonal balance
3) Low capacitance to maintain amplifier stability
4) A design that offers some form of resistance to RFI
With that in mind, the first cables that come to mind are something configured in a "Star Quad" configuration. Using this configuration will minimize inductance to maintain high frequency response, keeps capacitance at a very reasonable level so that the amp doesn't oscillate, offers some form of RFI protection and gives you a heavy gauge conductor without going to a heavy, less flexible gauge of wire.
You can find reasonably priced cables of this design at www.partsexpress.com under part #100-768, 100-770 and 100-772. Parts quality is quite solid for the money as they use 99.9% pure copper. The overall design equates to appr 11 gauge total, so it is relatively heavy. To keep things flexible, this design uses four 14 gauge conductors with you using two conductors for each polarity.
I would look into a 500 ft spool ( 100-770 @ $165 ) and bi-wire the speakers if at all possible. This will result in 11 gauge for the low's and 11 gauge for the highs. This should offer better signal integrity / less chance for RFI due to the seperation of the frequencies. You'll also end up with a total of 8 gauge for each speaker, keeping series resistance ( line loss ) to a minimum. This configuration matches your criteria in terms of budget and my criteria in terms of maintaining signal integrity.
Parts Express also offers quite a bit of variety in terms of connectors, etc... I would HIGHLY suggest requesting a catalogue from their website.
If you want to spend more money and go with "hi-fi" brands, you can also do a search for Canare cables on the Markertek website. Hope this helps. Gotta run.... Sean