Been doing some searching and cant seem to find someone who has installed a RNS-E unit in a MY98 A4 (B5) 1.8TQ? Do i have the space, and if not, is there a chassis i can purchase that would fit the unit?
From researching, you're not going to be able to get it into the current opening you have. You'll need an A6 version of the RNS-E as well as a center console update. You'll want to update to the 2000 to 2001.5 center console which houses the Symphony I unit. The A6 unit still won't be a perfect fit, but it'll be close. You can trim the face of the unit to get it in there.
I'm still trying to go this route too (I have a 99.5 with the concert radio). I've upgraded my center console so far, just need to take the big step of buying the RNS-E unit and planning for the parts I need to get it to work.