The double-chamber stovetop steamer doodad has an interesting problem, if you're into the technical side of this game. It produces espresso from steam, which does Bad Things to the coffee on the way past. Optimally, coffee (like tea, I understand) is best extracted at just below boiling. Most beans are best at 203-204F, depending on the roast. Steaming the beans ensures no crema (the light brownish coffee-foam that sits on top of a perfect shot of espresso) and a bitter flavor.
Now, if what you're looking for is the bitter flavor, then by all means, don't let me stop you -- go get a stovetop steamer. They're cheap and effective and simple. Further, if you're really into the bitterness of your black coffee, then you'd be disappointed by a perfect cappa anyway, especially because you'd spend an awful lot on a machine to make it right.
RedBeard -- I had a Gaggia for a long time, simple single boiler unit. Worked pretty well for making enough coffee to supply my room-mate and I, but a failure for entertaining. (shrug) But most people don't entertain with espresso. Anyhow, if you want a PID machine, I think there are several newer High End units that come from the factory with a PID installed. Otherwise, you'll have to DIY. It isn't hard, and the payoff is noticeable, but it does require some knowledge of electrical stuff.
But then, if you're enjoying the stovetop thing, then spending a bunch of money on a slippery slope may be a poor choice.
Enjoy.
Dan