Looking to try out open-back headphones. Advice needed.

Hi,

I'm looking at purchasing a pair of open-back headphones. I'm considering the AKG Q701 or the Sennheiser HD598. I would like to try them out to see how they compare the my current headphones, thinksound On1s. Does anyone perhaps know where I might be able to demo them? I'm based in Pretoria but willing to drive anywhere in gauteng.

I'm also planning on selling the thinksound On1 headphones once I reach the 50 post threshold.

Thanks!