try using venere.com and their map feature. any arond. up through 10 is just fine. i like to stay within a few blocks of a pair of metro stops(different lines).

5&6 are about as touristy as you can get. they are too touristy for me, and we usually stay in the 9th(which is also plenty touristy). staying on one of the islands is great. that's about as close to the center center as one can get.

the ACCESS guide to paris has very good maps and layouts for hotels, restaurants and activities. i circle hotels in blue restaurants in red, and go from there.

the hotel rooms in 5&6 are frequently hilariously minuscule. three days in paris is not much time. even 3 weeks is not adequate. if you can do a lindsey lohan(or whatever her name is) and lose your passport for a couple of extra days, do it.