You said the car is lowered, but not how much. Take a tape measure and go from the ground to the 4 jacking points on each side. If you have less than 5" you are asking for scrape city in many parts of the country.
Now as to swapping the wheels-you get the stock 16" ones and put something like the Bridgestone RE730/750 on them and you will be back to stock whell/tire size. Yes you can go with a taller tire-but the computer (ECU) will not love you. You can buy stock springs and raise the car to stock height-then again you can also get a set of Koni "yellow" shocks and set them down one groove to lower the car a little.
It is really critical to do the measurement I mentioned before you do any tire sizing. The stock wheels are just fine for the most part. As to CAMBER issues on a lowered car-they can be dealt with, for a price. Need help--drop me an e-mail. Been there with all of this.