You've complained that your previous bikes were too big.

The salesman has suggested 52cm.

You've stated the 52 felt perfect.

You're considering buying another too big bike for convenience's sake. And, expecting us to tell you this is fine.

Be patient for your right bike. If it fits you well, you might be inclined to keep it a while.

And, yes, you can change stem lengths by a couple centimeters. But, it's best to start with a frame that is as close to ideal as possible and then only make minor corrections for fit.