I am planning an upgrade to my 03 Sedan Bose system. In the end I want to have upgraded speakers driven by a 5-channel amp and a single 10"sub but keeping the stock HU and adding a PAC-NIS2.

From reading, it seems like the speakers are the best thing to replace to get a big improvement in sound quality. I am definitely going to replace my speakers but I am stuck with how I should do it.

If I am going to be opening up the interior to do new speakers should I just replace the Bose amp as well or could I choose speakers that I could install first and then add the amp later? I would be utilizing the stock wiring and just splicing into the connectors.

I already have a 5-channel (4+1 sub channel) amp but it doesn't accept differential inputs that the Bose HU outputs. If I were to use this amp I'd have to buy LOC (line output converters).

If my amp can drive 2 or 4-ohm loads, should I choose 2 or 4-ohm speakers? If my amp can drive 2-ohm speakers I may just replace the speakers now with 2-ohm ones.

If my amp can't drive 2-ohm speakers and I don't want to install the amp until later, how dissapointed would I be with driving new 4-ohm speakers with the Bose amp?

I'm probably making this way more complicated than it should be and I should just buy 4-ohm replacement speakers and LOC's and put everything in at once. That way I won't be ripping the interior apart everytime I want to do an upgrade.

 

I have done the same thing in my 03.5 Bose equipped sedan. I have the stock HU, Boston Acoustics speakers, 4080 enclosure, Alpine X-type 12 inch sub, and Xtant 600 watt 3-channel amp.

What amp do you have?

I think a LOC would drop the signal down too much for it to be useful. The Bose audio signal is 2 volts at the most.

you can power 4 ohm speakers with the Bose amp, but the volume will be really low.

 

Here is what I would recommend:
Buy a Rockford Fosgate 3sixty.1 or 3sixty.2. This will allow you to interface the stock Bose system, the 3sixty will accept differential inputs but more importantly you can install your amp and then use the 3sixty's eq and crossovers to tune the system and make those Bose speakers sound pretty good. The stock speakers are not too bad, what makes them sound crappy is the eq that Bose uses in their amplifier. This would be a good place to start your system.
http://www.rockfordfosgate.com/produ...s.asp?cat_id=1

 

The amp I have is by a small Canadian manufacturer; Ultimate Audio. It does not accept diff. inputs but does have 4 channels + 1 sub channel. It's a nice amp but the only way it will work in my G35 is with a LOC and if the LOC brings the input voltage down too much then I might as well just sell this amp and get a nice one that does accept diff. inputs.

 

There are other options for your balanced differential issue, such as a line driver. AudioControl makes nice products.