I was in this exact situation before.
Mac's are very resistant to viruses but…
I switched to Mac (pro,book and imac), but I kept 1 PC JUST for my music.
I’m huge on music. I’m looking to work behind the scenes in the music industry. And I have spent THOUSANDS on music through itunes, but itunes does not have everything, so I also use limewire.
I didn’t want to take the risk with my precious new Macs. Especially because I paid for them in full with my own hard earned cash.
So I’d recommend you keep a PC or get a cheap one for all the risk taking/crap and pictures that accumulate.
I guess it depends on how much music you're talking...
Hope that helps