A Hana DNA 40 is a good 40w mod. However, I found out, while using more RDAs, I ran out of power real quick. Therefore, I bought the Sigelei 100 Plus. Not disappointed at all. Next I'll get the Sigelei 150W. I saw a review of a German guy that had a Oziloscope hooked up to both devices, and the Sigelei out performed the iPV 150W, especially in the higher wattage ranges.
When buying your new device, make sure it has a self adjusting pin. The adjustable (the ones that you have to screw in/out) are ok when you stick with one top. However, it can get boring when you change the tops a lot and you have to re-adjust every time.