You are correct in saying that the Integy and the Quasar Pro are VERY alike. If the only thing that is holding you back from getting the Quasar Pro is it's noise, then you have nothing to worry about. The alarm is sorta loud, but I really don't know anyone who minds it. I kind of like it as a matter of fact. If you already have a PS, then go with the Integy 16X5V6, otherwise, go with the Quasar Pro as you will spend about the same on both and the Quasar Pro is AC/DC, but the Integy has a few more features.
Hope this helps,
etzkev