Upgrading RAM . Need help in selecting correct RAM frequency

Hello All,
I have a Sony E series Laptop (vpceb34EN). It currently has 3GB RAM. I planning to replace the 1 GB module with a 4 GB RAM module. But I am not able to find the frequency of RAM which mathes with the existing 2GB RAM. Below is the my RAM configuration shown by Speccy.
RAM
Memory slots
Total memory slots 2
Used memory slots 2
Free memory slots 0
Memory
Type DDR3
Size 3072 MBytes
Channels # Dual
DRAM Frequency 532.2 MHz
CAS# Latency (CL) 7 clocks
RAS# to CAS# Delay (tRCD) 7 clocks
RAS# Precharge (tRP) 7 clocks
Cycle Time (tRAS) 20 clocks
Command Rate (CR) 1T
Physical Memory
Memory Usage 51 %
Total Physical 2.92 GB
Available Physical 1.41 GB
Total Virtual 5.84 GB
Available Virtual 3.70 GB
SPD
Number Of SPD Modules 2
Slot #1
Type DDR3
Size 2048 MBytes
Manufacturer Kingston
Max Bandwidth PC3-10700 (667 MHz)
Part Number SNY1333S9-2G-ELFE
Serial Number 31371915
Week/year 43 / 10
SPD Ext. EPP

Slot #2
Type DDR3
Size 1024 MBytes
Manufacturer Hyundai Electronics
Max Bandwidth PC3-8500F (533 MHz)
Part Number HMT112S6TFR8C-G7
Serial Number 08445518
Week/year 43 / 10
SPD Ext. EPP

tRAS 15
tRC 20
Voltage 1.500 V

I am guessing that I can go for 1333MHz RAM. Am I correct ?
Can I buy any of these ?
Kingston DDR3 4 GB (1 x 4 GB) Sony Laptop RAM (M51264J90FR) - Kingston: Flipkart.com

Corsair DDR3 4 GB Laptop RAM (CMSO4GX3M1B1333C9) - Corsair: Flipkart.com

Please suggest me ..

Get the same Kingston that you have got in one of the slots.

So I can go for 1333MHZ RAM. Correct ? and I can buy this.. *linksredirect.com/?pub_id=54CL36&u...search&query=kingston%204%20gb%20laptop%20ram .. Correct ?

Should be fine I guess. I cant check the CAS of your existing RAM .....