well if those are your requirements then your choices are 325is/es/ix. although some non-sport 325i's had 2 doors during 1990. there was no 325is in 1991 except for the cabrio. i take it you dont want the 'E' engine either, becuase that performs on par with the 318is. your best bet would be getting a 1989 or newer 325is becuase that design is alot different and more modern looking than the 87, and more refreshed than the 88. 1990 was the first year for the airbag, and 1989 was the first year for the plastic bumper, sport package option, and only year for ellipsoid headlights, although some late 88's had the ellipsoids aswell. btw all 325is' 87-88 had the Mtech steering wheel, leather, sport seats, 3.73 LSD, basketweave wheels, and a rear spoiler. same goes for the 1989+ 325is' with sport pkg, although because of the new front it also came with a add-on lip.
100k miles is real good, even around 130-140k is good. just have a mechanic check it out and inspect it for any worn parts. dont much more than $5500 for a newer good mileage 325is, and the 87's can be had for around 3k with low mileage.