Yep. Exactly my setup. 2X200W into 4 ohms is the ticket. I'd keep things stock as to running them in stereo since the factory DIRAC is still controlling things. Not sure if they manipulate the bass stuff in stereo or the crossover point. XD400/4 it is. Mine is in trunk on left side panel for adjustment purposes. All wiring looks factory and hidden.
I just got my car back yesterday from the installation and it is 100X better. Crisp tight bass. Wow. Clear and much more defined. You feel the air too.
Even though one of my SWS8s has an issue!!! We had to get a new one and it will be here in a few days. For now, the driver side has the stock woofer and the passenger has the SWS8. Even with that setup, it is 100X better. Can't wait to get the other SWS in. The installer is a good friend and as soon as it arrives, he pop it in. The first one had a bad voice coil rub or misalignement. Speaker was scratchy.
Originally Posted by kaigoss69
Personally, I would go with the XD400/4 and bridge into two channels (200W a side @ 4ohm), and get the 4 ohm SWS-8. The underseat woofers play some of the midbass frequencies, and ideally you want these in stereo. However, I had them hooked up as mono before and did not notice any difference, but a trained ear might be able to tell (or if you have OCD you now must get a 2 channel solution
2009 Space Gray Carbon Leather E90 with DCT, Tech package, and EPS. Mods: Fabspeed 200 cell cats, Xpipe w/resonators and no secondary cats, BPM tune, Euro DCT software, Eisenmann Sport Mufflers, Vorsteiner Rear Diffuser II, SWS8 subs, JL Audio XD400 bridged 2X200W, built in radar