I guess Al-Khwarizmi comes from the near East and from 9th century or thereabouts, so there are no local stores for them to try out, but online shopping works perfect since they deliver to all places and to all times.

Being similarly tall with longish legs (especially my thigh bone, important for eg. legroom in cars, airplanes...), I'd be extremely weary of jumping on a bike that's not suitably sized, no matter what claims people make how a smaller bike can fit you.

But what matters just the same is your arm length, body length and such: basically, how far down and in the front you can reach when properly seated above the pedals? I've only got "average" arms (my wingspan matches my height), so smaller frames mean hard to reach handlebars.

When you can't easily try a bike out, if it's not rated for at least 2-3" (5-8cm) taller riders than you are, I wouldn't get it because your balance and posture will suffer.