If you are wanting new, it is hard to beat the Sherwood deal mentioned by markw. Sherwood makes some other receivers in that price range, which you might find on Amazon, as well as other stores, like:
Sherwood America Two Channel Stereo Receiver | RX-4105 (RX4105) | Sherwood America
Sherwood America 100W X 2 Channels Stereo Receiver | RX-4109 (RX4109) | Sherwood America
You might also want to look at Yamaha, which looks a little nicer, but starts at $150:
Amazon.com: Yamaha Natural Sound Stereo Receiver (R-S201BL): Electronics
And they look nicer as you go up the line.
If you don't mind refurbished, you can go up a step for not much more:
YAMAHA R-S300 Natural Sound Stereo Receiver
On the other hand, your father might prefer a vintage receiver, with a "silver" look to it (brushed aluminum), which is easier to read the lettering than all of these stupid black things that everyone makes these days. For some samples of what I mean, see:
Pioneer Receivers
The downside is that it will be more trouble to find what you want, with condition being very important in a used product, and then you need to concern yourself with whether the thing should be serviced or not. But he may well prefer one of these old units, as with them, one control does one thing, and with the brushed aluminum face with black lettering, it is far easier to read what the controls do. I have an old Pioneer SX-1250 that I plan on keeping for life. A lower model will have fewer controls and therefore be easier to use, but even something with as many controls as the SX-1250 is a lot easier to deal with than a lot of things these days, as each control does exactly one thing, and it is easy to see how all of the controls are set.
A few companies still make components with brushed aluminum fronts that are not painted black, but they typically are expensive. And they usually don't make receivers this way; only integrated amplifiers. Here is one of the less expensive models, which also happens to be very small:
TEAC A-H01 (Silver) Stereo integrated amplifier with built-in DAC at Crutchfield.com
What you should get also obviously depends on what your father will be hooking up to it. For example, if your father listens to LPs, he needs a phono input (unless he has a turntable with one built-in, which is more common now than it used to be). If he listens to CDs and not LPs, then he does not need such an input. And, of course, the amount of power needed depends on the speakers you are giving him, as well as how loud he likes his music.