Now I want one too. Do you need to cut a hole in the panel with the grill to get it to fit or is that opening just for better sound?

Referring to this picture:
http://i.ebayimg.com/images/g/FawAAO...cS/s-l1600.jpg

I am willing to bet you have to cut the hole to clear your sub. Otherwise they wouldn't include it. I'm guessing on that, but BSW didn't include one because they didn't have to. I made my own grille panel like that and the BSW setup sounds a lot better.

They may just be including it for sound quality, but I'm guessing they need the extra clearance for the 10" sub as opposed to BSW's 8".

Thanks - I kinda figured that as well, but was just hoping otherwise. I don't mind cutting the hole if it's absolutely needed for optimal sound quality but it would be nice to make that assessment first (i.e., listening w/ and w/o the panel on) before making the leap to cutting up the panel. Can anyone that's installed this, confirm whether the grill is needed?

The JL Audio Sub is 10" and fits perfectly in the side well and does not need a grill spacer as the one from RadioWorld. Essentially it sits stealth behind the OEM side well cover. If you chose to add a speaker grill then one could do this but is not necessary.

I assume you mean the JL Sub "Stealthbox" for E53's and not a 10" JL Subwoofer with eBay box from the UK in the original post? At $600 for the Stealthbox, I was hoping for a cheaper option that didn't sacrifice the panel (e.g., $100+50 for shipping the UK box + $100-150 low profile 10" subwoofer).

You get significantly better sound quality (+ a few db's as well) by cutting the hole in the panel. From my experience it also helps to reduce rattles in that right side area. For example, I used to get horrendous rattle from my fuel door until I cut the hole in the panel. And that's just the 8" BSW version. YMMV though.

Yes I am referring to JLs stealthbox. I picked up mine for $325. Yes the regular MSRP is pricey but a perfect fit and large enough subwoofer. I like a system that blends in with the surroundings of the X5 environment. If I were to cut a hole I would do as Crystalworks did on his application. A factory like integration

Got it. Nice find on the $325 Stealthbox (cheapest I've seen is $549). I hate the thought of spending that much money on a stereo upgrade to a 10yr old car, but I agree with the factory-like integration and OEM look. If I built the box myself it'd probably look like a 6-year old's birdhouse.

Apologies to the OP for "stealing" this thread. Lots of options to think about. Thanks.

I failed to think about the cutout! I'd prefer not to cut out the stock compartment lid. However to gain better sound I guess using a more stock looking grill would be ok. I personally think the grill they've used in the eBay listing looks terrible. Something along the lines of this might look better IMO:
http://www.woofersetc.com/media/cata...kte-10g_2_.jpg

Yeah that looks much more in line with the interior of the X5. If you are going down the route of cutting a hole in the trim, just acquire a interior side access panel from the wrecking yard and cut one of those and save the original for future vehicle sale. That way you get the best of both worlds.