Others have said it, but it is probably useful to summarize:
1) PCs are acceptable sources. Sonically the biggest issue with them is that they are not optimized for audio play back. They have inadequate DAC chips, they are prone to digital timing errors, capacitors are low grade, are prone to noise interference from the other functions of the computer, and other issues.
2) You need some sort of software program to manage music. Paid streaming services such as Tidal provide this. If you have music stored on a hard drive that you wish to play you need a program for that. Room is one service that helps you manage both in one space.
3) The OP has a DAC in his integrated amp and it surely will best the one in his computer. He therefore just needs to send the digital stream of the PC to the amp. The most common way to this is usb. Presumably the DAC in the amp offers other digital inputs but most computers tend to offer just usb as a digital output so his computer will probably be the limiting factor.
4) What is a streamer and should the OP buy one? Streamers are basically networking computers that have been optimized for sound. Some contain DACs. They also look like audio components.
The OP is obviously new to streaming. I am not familiar with his amp. McIntosh is a storied company. I can’t imagine that it would sound bad. Start there and stream from your computer. You may be so happy that you never feel the need to move on.
I used a computer into a DAC for several years before buying my first dedicated streamer. You can always upgrade later but since the OP already owns the amp and a computer it would be logical to start there