what kind of memory to upgrade a sys w/ 2x512MB

[flexy]

i got 2 older OCZ 3200 Platinum rev2 sticks w/ CAS 2-2-2-5,

i have them running in my dfi at 237mhz with a CAS of 2 which is great.

Now i might want to upgrade...either two more 512MB sticks....or maybe 2 1GB sticks....or maybe only one 1GB for now.

Any ideas what kind to get to keep the same overclock (if i am lucky ???)

I look around but the newer modules all have higher CAS latencies....

cliffs:

Want to add more sticks, maybe total 2GB or 3G
Want to keep my latencies (at least on the rams)

thanks