If all you are looking for is an inexpensive portable of dual conversion
design without SSB look at the Sony SW-35.
I recently bought one for use while doing chores around the house or
listening while I shave :-) It replaced an analog Tecsun 9700 which is dual
conversion but was completely deaf. It was cheaply built and the tuning
dial mechanism broke within 1 year - JUNK!

I didn't expect much when I bought the SW-35 but I find myself scanning the
bands with it almost every evening.
It has surprisingly good performance and is easy to use and master which,
IMO, places it on top of the budget end of portable SW receivers.


What's so special about a 550? Grundig?


Well if it was double-conversion one might expect better performance
(though it's no guarantee since it could be a badly designed
double-conversion
receiver).