I used an HQ-170 for several years (a long time ago!) The vernier tuning
(plus/minus 3 kcs, IIRC) was wonderful. Otherwise, based on later receivers,
it was not that impressive. The internal "hiss" level was higher than many
other receivers. (I worked 99% CW.) It had USB/LSB selectivity, but it was
not great. There should be no backlash. Some functions, like the noise
slot, were not very useful. Only later versions had 6 meter coverage; mine
did not. The clock was nice, but it was just a clock.

HQ-170s are relatively cheap on ebay. (I bought one a few years ago, just
for old-time memories, and sold it shortly thereafter. It does not measure
up to more modern receivers.)

HQ-180s (in reasonable condition) are not cheap. For general shortwave
listening, they are considered a high-end unit but this is a different
category than serious ham usage (especially for chasing weak DX with minimal
antennas, which was my HQ-170 experience).

As several people have mentioned, short-wave broadcasting is not was it was
a few decades ago and is generally disappearing rapidly. You can still find
the religious stations, if that is of interest.

I think your decision should depend on what you want to do with it. A good
HQ-145X should be ample for general short wave listening, unless you have a
very specific and difficult interest. An HQ-170 is ham-band only (without
WARC and maybe without 6 meters). An HQ-180 may be better for more intense
shortwave listening if you have specific objectives in mind. A good HQ-180
is likely to be much more expensive than the other two.

Bill - W2WO