Used Starter ht receiver.....5.1.....

Search out a Marantz SR18ex. A great older receiver that I've seen for as little as $500 ( retailed for $3295.) Weighs 50+ lbs and gives a solid 140 per channel. Built like a tank and sounds good to boot.
Denon has a few solid older HT receivers in their 5000 series that are excellent but cost more.
There's a few more. Look through older reviews on HT websites like AV Guide.
There's a good many more recent receivers going cheap. Not built as well as the older ones but decent non the less.
For the last 5 or so years, the Sony's are digital amps. They certainly aren't the horses of the past.

The older Nakamichi AV1(made in Japan) is a great starter and also a great finisher. Known for excellent musical ability and fantastic build quality. It
sells for 100.00 to 150.00 on Ebay. Also allows choice of
4 ohm speakers which many of the others can't handle. See
the reviews at audioreview.com. I've never felt a need for
anything else, though it's only about 100 watts.

Get something with Pro Logic II. This is one of the biggest improvements I've seen over the years. Other things to consider: stay away from receivers with different power rating for different channels, ie 60 right and left, 30 center and rear. This is usually the sign of an older unit. Also, keep the remote in mind. Some are much nicer than others. Many Denon, Rotel, Marantz, Sony ES and more will fit the bill.