Does adding 10 horsepower make a difference?

Not worth it; your stock exhaust system is stainless steel and will not rust out for 30 years or more. You'd need to remap the computer to make any improvement in perffromance with exhaust changes and that would also degrade mpg. When you change that to whatever they have in a muffler shop, you'll need to patch it every 5-10 years. That little car with 241 hp has got to be pretty quick as it is, and fuel frugal on top of that. Don't ruin a great car. Toyota engineers did a better job than Midas mufflers might try to do any day in the book. Your warranty is worth way more than a few HP in performance.

It will make a very nice car into an obnoxiously loud POS, for very little gain in performance. 10 HP is optimistic, and less than 10% gain is barely noticeable.

it will sound faster ....waste of money

No - you will never notice that extra 10 bhp which will only be produced at the top of the rev range anyway

A new exhaust system can run anywhere from $300 to $1000. Most "performance" exhaust systems just make more noise. NONE of them can actually GUARANTEE an increase in power. How much is a bit more noise worth to you?

That would fall under the more money than brains category.

It all hinges on the question: how often will you need more than 241 hp? If it is often enough to justify the price maybe you should examine your driving style.

A cat-back exhaust system usually adds 25 hp. Yes it's worth it. Don't get talked into replacing the cold air intake your motor came with from the factory for the POS Chrome cold air intakes with the cleanable filter. The oil on the filter migrates to the MAF sensor and will ruin it.