I own a 1990 Miata and and a1991 325i. I sold a 1993 325i to buy my e30. My wife has a 323i e46. All cars are 5speeds. The e46 is getting cheap but not in your price range yet. You know the Miata so I don't need to sell you on it. They can get tedious as DD especially if you have to have the top up. So i'll give my impressions of the e30 vs the e36.
The e36 is a nice driver. It has a quick steering ratio and the rear suspension is very stable. The back end comes around in a nice predictable manner. It is nicely balanced with just a touch of under steer. Steering with the throttle is smooth and easy. The 24v engines are really sweet. Nice fat torque band and the M50 has a rev happy feel to it. Mine had a noisy vanos that didn't really affect its performance but did make it less enjoyable to drive. Mileage was 22-24 mpg. in city traffic. The gear box in a 325 is a little weak compared the ZF in the M3 and 328i/s. The interior is cheap feeling and the door panels love to fall off. The headliners come down too. Watch the wiring going into the trunk. I enjoyed it more than my E46 and I still miss it (mostly the engine and the steering).
The E30 is more raw than the E36 and closer to the Miata in its interior noise level on the road. The E30 has a shorter wheel base and the rear suspension is "lively". The car has more under steer and the rear is less predictable. The steering ration is very slow compared to the Miata and the E36. All in all, it is more fun than the E36 but still solid and comfortable enough to drive on the highway. Although not as fast as the E36, the car has no trouble keeping up with other cars on the highway. The M20 is a stout little unit and has plenty of grunt (especially compared to the Miata). It really comes alive between 3500 and 5500 rpm. Not as rev happy as the M50 but still pretty smooth. Mileage is 18-20 mpg in city traffic. I also prefer the transmission and clutch in the E30.
As far as reliability goes, if both cars are well maintained, I give the nod to the E30. The E30 has superior build quality.
To me the E30 is like driving a classic car that is just modern enough to live with on a daily basis. I plan to add adjustable camber plates and perhaps a E36 steering rack in the near future.
About my Miata, "you'll have to pry it from cold dead hands". If I had to have just one car and didn't need back seats, Miata no contest.
