I would suggest if you go standup, make sure to buy a really good one as going up and down and supporting big monitors requires a strong desk. Plus you'll want to lean on it a bit occasionally (as I'm doing now to lighten the weight on your knees). The last thing you want is for your standup desk to come crashing down or to get stuck in the middle!

In Europe, I bought an Ergon mechanism and added an Ikea hardwood top 160 cm x 75 cm. By buying the top separately and locally shipping is much easier.