If you did want to do it...all the money for the mag wouldn't be from subscriptions alone. You could sell space for advertisements (they may be annoying but that is what will finance the mag). Just an idea.
Did you get the tensioner replaced as well? It's a good habit to replace that as well when you have a timing belt job done. Does it only run rough during idle or is it all the time? If it is all the time then it most likely is a timing problem. If it's just a rough idle it could be many things.
In my opinion, synthetic oil is a waste of money. For the cost of a synthetic oil change every 2500 miles you could change your oil with regular API approved oil almost every week.
Each material has its +'s and -'s. Urethane is durable and will resist cracking but painting it will be expensive because the paint has to be able to flex. Even though the actual bumper will be durable sometimes the paint will still "spiderweb" (the actual paint cracks not the bumper). Also...
If you lower compression you'll never make 200hp. The only reason you would lower compression on an NT motor is to turbo it eventually..in which case don't waste money on a header. You will get power from increasing compression if you are going to stay all motor.
I personally like 18's as well but since the rim you want is only offered up to 17...18 would be out of the question. You'll probably like the look of 17's better than your 15's. You'll just have to be more aware of what you drive over depending on the profile tire that you get too...