.com is much better for magazines etc unless if your mag is for a non profit edition/cause. You can try to find an alternative all together, i'm sure you can find another value name .com that is going to expire or already available. if you build your mag.org you are only making the .com more valuable to its owner and could be easy justify the $5k+ price. that's my opinion and good luck.
yes i think the .org or .net is enough, paying attention to the develepment of the site is the real deal