There's very limited choice on aftermarket head units that support the OEM DSP amplifier/speaker setup. It's the Dynavin N6/N7 and the Avin Avant 4 (the 3 has been discontinued). Assuming you are in the USA, then the Dynavin you must only buy from Jeff at J&T distributing in Fresno California as he's the only re-seller who properly supports these units for after sales care and warranty support. If you are outside the US, then it's pot luck on if the importer provides anywhere near Jeff's level of service. The Avin is also another USA only brand and the Avant 4 is due out soon. These units do have a close to OEM monitor look about them, but as is usual with these Chinese units, reliability isn't very good and at least on the E46 fanatics forum there's a significant number of owners who aren't/weren't happy with their units. Maybe the Avant version 4 will get it right?
Is there any pressing reason you wish to keep the DSP speaker setup? the general consensus is that the audio performance is mediocre, even when they were new! nowadays, given the time with UV impacts, heat/cold and wet/dry and general extreme conditions inside a car's cabin, those speakers will be past their best. If it's 'keeping it stock' thats the main reason, perhaps think about removing the oem stuff, putting in much better performance and sounding aftermarket products and if/when it comes time to sell, swap the oem stuff back in ?
Quality sound isn't usually associated with Aux in or Bluetooth Audio, however that is subjective. From what you say you want, then perhaps the GROM unit that has bluetooth audio streaming and phone calls capability might well be the product you need/want. I'd overall say to get a new modern head unit from the established and quality brands
2003 Ex-Police E39 530 Diesel Touring. Alpine White, 260,000+ Miles & climbing!
19" Hartge Nova 5 - with custom painted 'Flash Chrome' centres & Polished Lips (set of 5)
19" Hartge Nova 5 - Awaiting custom re-finish (set of 4)
19" Hartge Classic - with custom powder coated centres in shadow chrome & diamond cut/no lacquer lips (set of 5)
20" Hartge Classic - Awaiting custom re-finish
19" 3Pc Forged wheels - ID retained until re-built & finished (2 sets)
20" 3Pc Forged wheels -ID retained until re-built & finished
19" Centres - ID retained until rebuilt & finished
Full Custom Audio install - Arc Audio KS Mini ampliifers. DLS 5.25" 2 way front components & 4" 2 way co-axials. JL Audio 8W3-V3 subwoofer in stealth enclosure. Parrot Asteroid Smart head unit, custom door builds for DLS front stage & Earthquake SWS6 flatline subwoofers, custom rear pillar speaker pods. LumiDock iPod dock,
H&R Springs, ExoticsTuning front lip spoiler, Sport F/R bumpers upgrade, Carbon Fibre effect printed Vinyl roof wrap, High gloss black vinyl window trim wrap, Hartge bonnet/hood & tailgate badges, rear rooftip spoiler, matt Black kidney grille, projector foglamps.
Hartge auto gearlever, Hartge Handbrake handle, Hartge door sill strips, E46 M3 CSL Alcantara/Tri-stitch SMG steering wheel, full Black Leather Sport seats,
Custom ECU re-map biased for more Power & Torque in Steptronic mode, EGR delete, K&N induction kit, Stainless steel de-cat, Stainless steel exhaust backbox with twin oval pipes. Manual 5 spd gearbox conversion.
Plenty more modifications to come!