I'm trying to build a decent sounding budget system for my '04 X (non-premium HU). I'm leaving the HU for now to save for a DD kit and DVD/NAV. I have decided on the following components based on reviews/price:

Fronts: Phoenix Gold RSD components (2x60 RMS)
Rears: Alpine Type S coax (2x50 RMS)
Subs: Memphis PR 12" (2x250 RMS)

I have basically been learning car audio on the fly while trying to build this system, and am having trouble figuring out the best way to power everything and maximize performance vs. cost. I was originally going to just go with a 5-channel amp but it seems I might be lacking in power for the two subs on the 5th channel. Can I use a 3 or 4 channel amp to power the components and subs and run the rear coax's off of the HU? I know rear speakers are not very important in the coupe but how necessary are they in the sedans? Any help is greatly appreciated, I can't stand the sound of my stock system anymore!

 

I just went through all of what you're going through, so take my observations for what they are worth:


Those PG RSD's can handle more than their rated power, some people on other forums have used upwards of 150 watts per side with no distortion. The system I heard these speakers in had 100 watts rated (probably 120 in real life) per woofer and maybe 50 watts per tweeter in an active setting (where each speaker gets its own channel).

Rear fill is something that is purely up to each specific person. I don't mind it, but many purists leave it out completely. They liken a soundstage as having all the sound coming from the front ala a concert, and rear fill would be unnecessary. Regardless, running stock rear speakers with HU power first seems to be a good cost efficient move and if you want more, go ahead and get some good coaxes.

With one sub, you could've gotten a 4ch amp, used 2 channels for the fronts and bridged 2 channels for the sub. With two subs, however, I'm not sure if there are all in one amps that can do that. I think I recall seeing Bing (screen - 16psibrick) using a DLS 5 channel for 2 subs, I'm not sure.

With two subs, I'd personally use a separate sub amp. Are those subs 1 ohm stable? If so, I was planning on using an AudioQue 1200D (http://www.audioque.com/aq/AQamps.htm) which is only $249 shipped. It can go to to 1200 watts RMS into 1 ohm, so 600 watts can be avail. per sub. I'm always of the mind that more headroom is infinitely better than not. BUT the other mindset - usually for cost and or space limitations - would go for an all in one amp and possibly one sub.

Good luck, I'd imagine you would have a capable installer who could guide you more in-depth than the points that I brought up briefly.