You know, the only e-cig purchase I regretted was my 401. Oh, it's a nifty looking e-cig, and it's fun to vape, but, as you noted, I generally don't get a particularly good hit with it, even with high nicotine liquids. Moreover, I found it bothersome to deal with the itty-bitty cartridges since I'm a heavy vaper . . . more trouble than it was worth to constantly pop the cartridge with a straightened paperclip to refill. I occasionally dipped the atomizer, and that worked pretty well, but with so many other way cool models out there, I just put my 401 up in case of an emergency.
If you're looking for something that still kind of sort of feels like a cigarette when you hold it, you should look into the 510 with MANUAL batteries. The battery life isn't the greatest, but the manual battery and the 510 atomizer pack a very nice punch.
If you're thinking that you're not terribly tied to the idea of vaping with something that looks like a cigarette or a pen, then you're ready to walk on the wild side. You can try one of the Big Five wv2win references in his post. I have a Screwdriver and a JantyStick, and I love them both. At about 3.7 volts, both provide a strong vape and longer battery life than any of the "traditional" models. And surprisingly, they're not nearly as large as one might think.
And if you're really looking to step things up, the GG and the Prodigy offer vaping at even higher voltages. I don't have much experience with really high voltage vaping, but I'm sure you'll find TONS of information if you search the forum.