I've had my '98 ZX2 for three years and love it still. The 2000 model was supposed to be the last year but Ford started selling more of them. Focus was the replacement but the Z is still in production.
I don't know about the better factory stereo but my cheap one is that, cheap, but sounds ok for the time I'm in it. I have an automatic and if I remember correctly at 70-75mph it tacked about 3,000rpm's. There's quite a lot of after market stuff out there, but not as much as the Focus has. Intakes, exhaust, UDP's, header's, plug wires, Accel coils, lowering springs etc. There was an S/R model made in '99(110 of them) and 2000(2000 of them) that had about $4,000 worth of mods from the factory. You might still can find a new or almost new S/R.
Mine's basically stock except for the Accel coil and a Magnaflow muffler. The car has been the most dependable new car I've bought in a long time.
If you're in to running it to death, the tranny could give you problems. Thats the weak link. Normal driving my tranny has given no problems except you have to flush the atx fluid around every 15,000 miles to keep it that way.
From what I hear the 2,000 model will be the last. There's still no better car out there for the money than the ZX2. They perform and handle well, especially the manual transmission model.
I only have 14,000 miles on mine and average 24 city and 34 highway with the a/c on.