There are tons of good samples on the internet most of them of better quality than vinyl.I love vinyl so for me to say that says something.Alot of the sounds you will find sound alot better if you just sample them from your computers soundcard into your MPC.Try
www.killerbeats.com for starters there's lots of usefull stuff on there.I've got a whole list of sites that have sounds on them.I treat the internet the same as I would digging search ,search ,search.Also there are lots of sites that have Radio Stations and things where you can listen to music.Don't be scared hook up your MPC to your computer and sample away the deciding factor will more than likely be the quality of the outputs on your soundcard.