Looking for a High End SQ Install - E39 BMW 5 Series

What size of comps are you looking for? Also what brands are available to you or are you buying everything online?

 

tall order. do you prefer matching equipment? like do you care if you have two or three diff brand amps?

as for a head unit. i know pioneer just released their new stage 4 stuff. bad ass head unit.
dual 31 band eq, insane crossover slopes for sub, midbass, mids and highs. it's 1400 US tho, but very nice.

i think a nice 3way set up up front will do better, and you wont need rear speakers. the midbass should come from up front anyways. you could always run the stock rears off of head unit power for rear fill if you want fill.

a true SQ vehicle normally doesn't use rear fill. not saying its wrong but some just don't. if you must go with a rear fill, a reg set of decent coaxial speakers should fill the bill.

the port thru the rear seat is a good idea. i've seen and heard ported, sealed, and IB set ups each sounding great in their own install. i want to say for a flat response go sealed or IB. deep bass extension is just insane and from the set up i heard can get punchy too on the kick drums, but you'll need a good midbass to back it up too.

you can deaden the **** out of your doors and run a mid bass in it and get some kick panels to mount your mids and highs. with the right color carpet it can look pretty stock.

also going for the stock look you can mount your subs in the rear deck if you do IB. you wouldn't even see them if done right. 2 tens should fit the bill, or even 2 8's. im sure your vehicle is pretty solidly built, so sealing the truck shouldn't be an issue.

you can save a lot of cash if you don't need to buy a ton of wood, and or rear fill speakers. that money can go torwards a good 2 way or 3 way front stage and 2 nice subs. a good 4ch should fit the bill too. 100 x 4 should be just right if your car is as quiet as a church anyways. less power needed to over come road noise.

ive heard good things about some parts express speakers.

a friend of mine runs dayton 7 in mids in his corolla doors and pioneer tweets. vert nice combo for very cheap. he did go the extra mile and have custom built passive xovers made for them.
http://www.parts-express.com/pe/showdetl.cfm?Partnumber=295-374
http://www.mcmelectronics.com/product/55-2421&mybuyscid=12800730750
i found these on accident and the specs and price seem very doable for a nice simple install. i bet 4 of those with 50~100 watts each would easily fill your cabin with enough bass to satisfy most musical tastes.

you can look into peerless, vifi too as good sounding mids and tweets. all these are more do it your self tho.

hope i helped a little bit.