Is 8gb enough for a mp3 player

depends on two factors...quality and how much of your collection you want to bring with you.

the greater the quality of the file the better it will sound generally, however as quality increases so does file size so you will be able to take less files with you.

if you have a collection larger than your mp3 capacity you will have to swap out songs that you want to take with you all the time. up to you to decide if this is a hassle.

i'm currently using an 80gb ipod classic

25gb used
3,125 songs

most are 192kbps with a few 256 and 128 depending on how i purchased them.

perhaps this will give you a good estimate!
Assuming you are encoding music at 128bps that works out to approximately 1MB per minute. 256bps would be approximately 2MB per minute. That works out roughly to be either 8,000 minutes of music or 4,000 minutes of music.

Assuming each song is 5 minutes long, that means with 8GB of storage space, you can store approximately 1,600 songs @ 128bps, or approximately 800 songs @ 256bps.