something fun, special, reliable, quality

It's very hard to find good steering in a recent car. I like the EX, but its steering is fairly numb. The steering in the related G35 / G37 sedan is a little better. But still far closer to your IS than your 240SX.

The 2014 and up Mazda6 might have the best steering among mainstream midsize sedans, but it still feels like a midsize sedan, and so not nearly as sporty as the 240SX. The smaller Mazda3 feels more agile. Then again, it will probably be hard to find either as a 2014 within your price range.

Instead, I'd advise another coupe.

The Scion FR-S and Subaru BRZ (essentially the same car) can be a lot of fun. Owners have reported some problems with them, but nothing major, and most should have had these problems fixed by now (a chirping fuel pump, an uneven idle, tail light condensation). The main downside for these cars is that they're too noisy on the highway. Around town, no issue.

If you do want to trade some sportiness for lower noise levels, look for a 2013 or newer Hyundain Genesis Coupe.

I've checked, and it's possible to find 2013s of any of these for under $18,000.

I'd also suggest a Mazda Miata, but it has no rear seat.

I personally own a Mazda RX-8, and it steers better than anything but the Miata, and is far more livable on the highway than the FR-S/BRZ, but fuel economy is poor (high teens suburbs, low 20s highway) and reliability is iffy. Cheap to buy, though.

Ah, the best of the first-gen IS300s...if only it were offered with a manual :)

Since you're looking for a wagon, the EX might be your best bet. My wife really liked the one we had for a week a few years ago (I haven't driven one more recently). The main disadvantage is that they're about the size of an IS 300 inside. Which probably isn't an issue for you. And the slightly higher ride height might be a good fit.

One other possibility: Acura TSX wagon.

I never found the Mazda6 all that fun, too large, but your impression could differ. Worth a look if you can find one to drive.

I don't have much to add on those cars nor much beyond what Michael said, but I agree that you won't find steering like the 240SX in anything recent. I learned this a few years ago when I was test driving about anything I could find with a manual transmission that looked somewhat practical and engaging. Everything felt numb compared to my aging 2000 Accord Coupe, and I was particularly disappointed with an Infiniti G35. (I even found a sedan with a manual transmission and really wanted to like that car, but I didn't. However I did test drive a BMW 328i a couple nights before).

I wound up buying a 2012 Mazda 3 (then new), which has some steering feel, and I really like the car, but I'm not sure how the new ones are. If you come across a well-maintained first gen (I think up until 2008) Acura TSX, however, you may want to take a close look at it. It's a nice cross between fun, luxury, fairly roomy without being a barge, and still some decent steering feedback. I seriously considered a 2008 model, but I wound up getting the 2012 Mazda 3 instead.

Have you driven the Mazda3 and EX yet?

Another possibility is the Mazda CX-3, which will be available in the fall. One other reviewer said it reminded him of the Mazda Protege5, which had the sort of steering and handling you're looking for. (But I'll personally be surprised if it steers similarly.)