Imagine how you'd feel if you'd bought the DSP system and felt the same way...
The X5 system has some strengths (actually, mostly POTENTIAL strengths) and some definite weaknesses. If the Sirius sounds that bad I'd get it checked out.
But in terms of overall SQ, the mids and highs tend to sound harsh and grainy and the lows are underpowered.
There are two ways to proceed.
The BMW OEM amp has front door woofer, front 2" mid, and front tweeter channels, and rear door woofer and rear mid channels. Each channel ONLY plays the notes that are assigned to that speaker. For this reason, and for the reason that no big-name speaker company makes a dash mid that will fit into the dash AND play the notes BMW wants it to play, replacing any of the front three-way speakers in BMWS is problematic.
BSW (an approved vendor on this board) has one solution, which uses their replacement midrange. This is a pragmatic solution which probably gives you the best performance you can get with the factory amp (which is still a bottleneck for performance- how much so is a point of contention: ).
We would recommend replacing the OEM amp (or at least the front channels) and replacing the three-way system with a good-quality 2-way system.
Here's how we responded to a recently-posted request for a recommendation:
OK, here's my professional recommendations:
1) You can get great sound in the X5 while keeping the OEM HU. The Icelink works with the OEM HU.
2) Get two Icelinks and one DSP kit for the E39. It's worth it. Nothing else even comes close for BMWs.
3) I am pretty darned good at invisible X5 audio upgrades.
Level one is to upgrade the front speakers and get a 2-channel amp for the front only, retaining the OEM speakers in the rear doors. For something worth doing, you are looking at about $500-850-1250 in gear (depending on gear - that's DLS in the middle and Dynaudio at the top) and about $250-300 in installation by a shop that OUGHT to be taking your car apart.
Level two a is the above plus a 3 or 4-channel amp, and an 8" or 10" sub hidden in the passenger rear side compartment. That bumps you to $800-1200-2000 in gear (similar progression) and $750-1000 installation and fiberglass fab charges from a pro shop (hidden everything).
Level two b is a four channel amp and new front and rear door speakers. $750 in gear for good stuff worth upgrading to, $300-400 installation.
Level three is front, rear, sub. Hard to do for less than $2K with stuff that's worth buying, figure somewhere between $2500 and $5500 installed depending on the level of gear you select.
The best sound for the money is 2A. 3 doesn't sound better than 2A, but it sounds louder (depending).