found an interesting aftermarket radio with the nav and whatnot that actually fits nicely into the E34 platform... perhaps, the E36 and E38 as well... I can't justify the $800 pricetag though...

Becker Cascade BE7907 CD MP3 Aux in Bluetooth Navigation Voice Control | eBay

disclaimer - i am not affiliated with the seller by any means, this listing came through my automated search on eBay