Ugh. Both of those cost money, neither look as good as Zen Cart, and it looks like you have to set them both up yourself.
A good rule of thumb for the Internet - whenever you're tempted to spend money on something, check first and see if there's something free and open-source out there that'll do the same job, but better.
Getting a warehouse to ship products directly to your customers for you is known as Drop Shipping. On the one hand, you eliminate a lot of hassles that come from keeping stock in your garage or spare room - and on the other, you do end up paying a little more for your stock, and returns can get complicated. I've got a couple of mates who've tried it and done fairly well, but I haven't tried it myself so I couldn't say one way or the other.