Hi Ya
If you are still looking to buy speakers for your R33. I have 2 pairs of near new Alpine 6 1/2 in Coaxial 2-way speakers 90watts Peak Output.
They cost me $299 a pair and I thought a fair price would be $150 per pair if you are interested.
I had them installed in a R33 GTR for about 3 months and this was the biggest I could install in the back.
If you are interested I can be contacted on 0407 883 263.
Regards
Duane