Can get a Koyo radiator (not racing model) for $240 with plastic tank and copper core, also saw advertised a no name brand of aluminium for $183.
What's better??Aluminium or copper core with plastic tank??
Not saying I will buy either at this stage, but when the time comes (soon) what should I go for?

This is a tough question, neally all new cars are using the plastic radiator as it is cheaper and lighter than the old full copper ones, i don't know to much about aluminium ones but i'm guessing there simular to the copper except lighter and better at cooling due to aluminium's properties. The problem with plastic radiators is that the don't last to long, 3-4 years and you might be facing a crack in the radiator, usually most commonly occur on the top half where the top hose connects. But it all depends on the rest of your engine. The aluminium one will last you a year or two longer, and be a bit more expensive to replace (unless you get a no name one as you mentioned). so its really up to you, no big difference (unless it is operating in hot conditions all the time), especially if you have a 4 banger, but if i can give you a tip, don't buy generic (no name) parts, its just not going to last and will effect the performance of your car, a good aluminium radiator should be around the $250-$300 mark not $180.

Copper has a better thermal conductivity than aluminium and is harder and therefore less likely to be damaged by stones.

There are a lot of Magnas around with their original plastic tanked radiators so their life is not that bad. My 93 TR still has its original.

Rob

I have an Aluminium Radiator in my 2nd Gen.
See this thread for more information...
http://www.aussiemagna.com/forums/showthread.php?t=41608

No problems so far - even on hot days with the A/C on.