Don't waste money on speakons if you already have perfectly functional 1/4" speaker cables. I doubt you'd notice any difference until you're really pushing those cabs to their limits (which would be "liquify your liver" loud), and maybe not even then.
Of course, if what you have now is some cheap, high gauge cable only suitable for 100w beginner PAs, then yes, an upgrade might make sense. I have some pretty hefty Live Wire 1/4" cables that are about $25/ea for the 5 foot version. They have heavy duty plugs and I think they are 12 guage, and I would have to run them about 4 times as hard as I do now to feel like they were the limiting factor.
In all but very rare cases, you'll probably run out of speaker before you run out of cable.
Just connect one cab to each side of your amp with your existing cable (unless it's really low quality), and you should be fine. Save that $50 or so for something more necessary and/or fun (like strings or some kind of pedal).