| I'll go ahead and say it, read the newbie links first. Then try to find a local luthier who can help you select the right bass and do any work in the future (and you can count on some work needed sometime down the road). if you buy new, you will ABSOLUTELY need a setup done. If you buy used, it will depend on how the previous owner had it set up. Out of those basses you listed, the shen would be a good buy. If you can spare the change, you should go for a SB100 over the SB80. The 80 has a maple laminate top whereas the 100 has a spruce laminate top.
Oh one more thing, GET LESSONS!! It will save you strife and possibly any permanent injury/nerve damage. I think everyone else here will echo this. | 
