Get some leathers and head to the track. You won't be bored for long.
The 520 chain/sprocket conversion kit weighs less, therefore, has less rotating mass than the 530. This allows the motor to use less energy to spin the wheel, creating a faster acceleration rate. For the street, it isn't really necessary, and performance gains will be marginal at best.
Going up one tooth on the front, or a couple on the rear will give you a more noticeable "power" increase. All that is really doing is slightly decreasing the amount of revolutions the front sprocket has to make to spin the rear wheel. Given the same amount of power from the motor, the wheel will spin faster due to the decrease in the revolutions.
Remember if you want to go up more than a couple of teeth in the rear, you might have to buy a longer chain.
More teeth = quicker acceleration
Less teeth = more top end
Jetting is somewhat of a "black art" still. You can get it close if you are good, but the bike will still need to be set up on the dyno for maximum performance. Jetting involves fuel/air mixture. As a rule of thumb, the bigger the jet, the more power the bike will make. HOWEVER, that is not always true. Several bikes I know of ran BETTER and made more HP/torque gains when the jet size was DECREASED. There are so many ways to set up and tune a bike (airbox, filters, porting, cam timing, idle circuit, pilots, mains etc.), and for brevity's sake, I'm not going to go into it here. Find yourself a good dyno tuner (preferably w/a 4-gas sniffer), and shell out the clams to get your bike set up right. You'll be glad you did.
A combination of jetting, re-gearing (changing sprockets) and dyno tuning will most likely give you the best results for the cheapest price. After that, engine mod$ will have to be the next $tep if you are not $atisfied. $$$