Since they were sold by World Wide Stereo and Fullfilled by Amazon, just return the P153 for FREE RETURN and get another P163.
The one reason I buy just about EVERYTHING (fullfilled) from Amazon is because of their #1 awesome customer service.
All you have to do is go to your account, then on your order, click the RETURN ITEM button. Then specify which speaker you are returning. In this case, for example, I would return ONE P153 speaker. The reason is "Not as described" or something like that. Then print the Pre-Paid UPS label. Return it to Amazon with free pre-paid shipping. Order another P163 now while it's on sale. Track your return of the P153. Once amazon receives the P153, they will credit your credit card.
Or just contact Amazon if you don't want to do it yourself. You will still have to print out the pre-paid UPS label yourself.