The Dynomax VT does have issues w/ the flaps rattling.
The Dynomax super turbos are much quieter, but hurt the power. Yes, it is noticeable.

The Dynomax Ultra-Flow is a good choice. MORE flow and quieter than the Flowmaster 40.
The Hooker Max Flow is basically the same thing as the Dynomax Ultra Flow.

The Hooker Aero Chamber is a little quieter than the Ultra Flow and Max flow, but louder than the turbos. Still make great power though.
These would be my choice if you want power, but reasonably quiet.

CHIP
'70 hemicuda, 575" Hemi, 727, Dana 60
'69 road runner, 440-6, 18 spline 4 speed, Dana 60
'71 Demon, 340, low gear 904, 8.75
'73 Chrysler New Yorker, 440, 727, 8.75
'90 Chevy 454SS Silverado, 476" BBC, TH400, 14 bolt
'06 GMC 2500HD LBZ Duramax