The only reason I built something to reach the full wattage potential of the iPV3 was just for kicks. It's not a very good vape. Also, building your own coils is currently the only way you can pull it off. Due to the voltage limitations of the iPV3, you need resistance of .33 ohms or lower to actually get the full 150 watt output.
On a non-rebuildable tank with 2.0-2.4 ohm coils, I would think anything above 7-10 watts would result in some nasty, burnt flavors. There's no reason you can't still use an iPV3 with that kind of setup...in fact, you'd get incredible battery life. If you don't want to get into rebuilding, maybe check out the Aspire Atlantis clearo. I hear they are super, but you'd still get nowhere close to 150 watts (supposedly they like around 30-40).