I'd buy a used Browning A-5 if I were in your shoes. They seem to sell for about $550 around here. I have had one since I was 12 years old (67 years) and it has never failed me.
I'm a Browning A5 junkie, and I really wouldn't recommend one to any but the most hardcore gun nuts (like you and I)
As great as the A5 is, modern shotguns are cheaper, lighter, and way more versatile. Also, any A5 you find for $550 has probably been ridden hard and not maintained well. Very good condition Light 12's start at around $1,000, and 20 bores in VG shape start at about double that. The middle gun below is a 1973 Belgian I recently found that was NIB, and it was a steal at $1,100. Enough of steal that I couldn't walk away from it.
Most A5's have fixed chokes, but very late models have interchangeable chokes. A5's do not have chrome lined barrels, so steel shot isn't recommended. They also won't handle both 2 3/4" and 3" shells, its one or the other. Modern shotguns can use both shells interchangeably without any adjustments, just load and shoot. Lastly spare barrels for A5's are VERY expensive, starting at around $350 for a plane no rib barrel in okay shape, and expect nearly double that for a good condition barrel with vent rib.
All that said, I personally use an A5 almost exclusively. I too fell in love with the A5, also at age 12... My hunting buddy had one and it was just the coolest shotgun I had ever seen. 40+ years later, its still the shotgun I'd rather be shooting, and I really don't care if something "better" exist.