Wow, 70 bux for an o-ring chain and sprockets!! I was going to say about twice that much would be a good deal....depends on the quality of the sprockets.
No one here is going to be able to give you the perfect answer...just some direction. What size tires are you running?? How heavy are you?? How do you like to ride?? Those are all things that come into play when dealing with gearing.
If you're happy with your tire size, I recommend just buying a new front sprocket or two...go up and down in size, and see how they feel for you. Once you decide what way you want to go, if you want a tiny bit more fine tuning you can do that with the rear. Then decide on a gear ratio and get a nice chain and sprocket!! Always lube em up....and don't even consider anything less than an O-ring chain!!