Thanks Rob, that was very helpful! I have a much better idea now about which versions of each chip I should I get. I ordered a some samples of the LME49720NA from National Semiconductor as some people have suggested (thanks leeperry). It's a steal considering I didn't have to pay anything (free shipping) with my .edu email address.
You quickly see why many think they sound the same even before testing. After testing, some say yes and some say no. Your ears...