I theory yes and the law is behind you but that doesn't mean that its good practice and as mentioned above can hurt the business.
But I understand where your coming from as I recently had the same problem with a guitar amp, I wanted to try several models and see how the sound with my gear but I would have had to order them and return all but one to do so, its the one downside of online retail. In the end I went to the local stores with my gear and tried as many as I could before buying one from the stroe. I didn't get to try all my list but it was something I couldn't buy unseen, it was more expensive than online only retailers, but I was happy to pay a premium to see the item in person first, it also probably cheaper than returning 5-6 40Kg amps. Try and go to local stores and try before you buy or talk to friends and see if you can borrow theirs instead of filling up the OC warehouse with B grade stock