I think the iMac, especially a refurbished one, can be so much more than a new PC which would be the price of a refurbished iMac anyway. To me, it's a no-brainer.
The Mac, due to it's OS is somewhat safer than a PC against viruses. But in reality what makes the Mac OS far, far safer is that it is too small a target for virus writers and this will make any Mac virtually virus-proof.
I have used Apple products since 1979 and never got a virus until a few years ago, and even then it was rare as an occurrence. I have had a few PCs, and got hit by viruses much more requiring me to reinstall Windows. I found that no fun especially since I was a PC tech (MS, Dell, HP) for 8 years as well as fixing Macs, and mostly had to deal with PC/Windows viruses on a mass level sometimes fixing hundreds of machines. I would not want to deal with a PC if I wasn't a tech since I can see what can crop up and attack Windows.
There is also something to be said of the time you save using a Mac vs. troubleshooting a PC. A computer should be a tool, not a hindrance. That being said, Windows has come a long way but is still far from OSX.
Another great, cheaper option is the Mac mini and it's what I use everyday.