A048 are superseded. Current Yokohama is A050 - that's what Improved Production has been using over here for the past few years. The A048 wasn't a great tyre - slow and loses even more performance with heat cycles. A050 on the other hand is regarded as the fastest semi available, along with Hankook Z221s.

R888 is also not a great tyre IMO. The wear well, but had no grip for a semi slick.

I'm currently using Nankang AR-1 semis on both my cars - twin turbo Soarer and AE111 Levin BZR. On the Soarer which I've owned for years I've had a few different semis now:
Nitto NT01. 245/40 R18. Lakeside 1:01.3
Hankook Z221. 235/40 R18. Lakeside 59.8
Nankangs AR1. 265/35 R18. Lakeside 1:00.2

So as you can see it's not a straight comparison using the same sizes, but the car was unchanged so it gives you an idea of how they compare. My Impressions:

Nitto are made by Toyo in the same factory in Japan, and have the same construction and compound as R888. They were unimpressive. lacked lateral grip and drive. They were only 0.7sec faster than normal road tyres! Same kind of performance I got from the R888 I used on a 180SX years ago. But they were cheap. That's why I tried them, combined with some people swearing they were better/faster than R888 - which they weren't.

Hankook Soft compound Z221 were awesome! So much grip it was ridiculous. But only lasted 5 track days so not great value for money, but if the ultimate goal is going fast, these are awesome. Hankook Z221 and Yokohama A050 are generally regarded as the fastest semis currently available. When I say they only lasted 5 track days, they still have plenty of tread, just lost grip. They didn't taper off - they stayed rocket-ship fast up until the day they gave up the ghost and went over 1.5sec a lap slower.

The Nankangs have good grip, good wear, and great prices. They're available in 185/60 R13 http://www.ebay.com.au/itm/Nankang-AR-1-185-60R13-80V-80-TL-Tyres.
When I got the Levin, I went straight for the Nankangs. If you can get them in NZ, give them a go. They're not widely available in Aus...