My Sirius sounds the same as the radio to me, but I agree, it's not the best sound system compared with some others. Lots of folks have been upgrading - try doing some searches and you should find plenty of info. Also, check out this article - I have mine set this way and it does sound a bit better... GL!

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'08 335i Coupe - Barbera Red / Saddle Leather / Light Poplar Wood / 6spd Manual
Options: Sport, Premium, Cold Weather, Comfort Access, Active Steering (awesome!), Power Rear Shade, IPod Adapter, Navigation w/IDrive
Mods: M6 Wheels, Split Armrest, M-Steering Wheel, Euro Light Switch w/Rear Fog Lights, Short Shift Knob w/Matching E-Brake Handle, Clear Reflectors, CDV, Clear Bra

Retired:'04 X5 4.4i