Questions on '86 5000 CS Quattro

[zuofeng@castor.wustl.edu (~{Ws7g~})]

Hi netters,

Having been driving an '84 4000S for the last 5 years, I am toying
with the idea of replacing it with a Quattro model.  The only one
that showed up in the weekend paper was a '86 5000 CSQ with 
98,000 miles on it. A little better than my 4000's ~110,000 miles. :-)
Asking price is $5,000.

I went to look and drive the car in the morning. The car's in very
good condition with just one scratch on the paint and one cut of some
sort on the driver door molding. 

Things that don't work include the power antenna, the rear speakers
(which apparently broke in '91 and the owner simply lived with it
since). 

Driving impression: the car appears pretty solid, although making a bit 
rumbling over rough pavements. Big difference from my 4K is in overall 
feeling: the car felt somewhat ponderous.  

Are the later year 5000/100 models better in that regard?

The owner had the steering assembly replaced 2 years ago. Up to 60K mile
service were apparently done at dealer and later ones seem to have been
done at local repair shops.

The rear door power windows don't open. Is there a special
switch for these? I tried both the driver-side switches and the
ones on the doors.

What others should I been on the lookout for?  The turbo does make
some whirling sort of sound. How do I tell it's working OK?

The brakes felt hard with little travel. Is it normal for the 5000 CSQ
with ABS? Also I heard that ABS' are supposed to make chattering sound 
when you turn the car on. Does the 5000 CSQ's ABS do that?

Does the timing belt in the car need to be replaced at regular intervals?

Finally, is the asking price of $5000 for the car reasonable?

Thanks much for all your suggestions and help.

ZL