I personally would not pay double for an spot-welded-on heat exchanger. That may matter on the approach to Everest, but generally there are much better places for your hard-earned cash.

If you want to experiment with heat exchangers, buy a roll of heavyweight aluminum foil and experiment with the pots you have. You would be amazed at what you can do.

Respectfully, I'm saying that it's not what you buy, it's what you know. And there's only one way to earn that hard knowledge: go out into the field and actually use stuff -- even if it's $0.99 from the Sally Ann. Over time, you'll go through some gear that actually works (to your utter surprise), and some that is sexy in theory but just doesn't get the job done. That's the only way; there is no shortcut.

My $0.02.