Identify SPD RAM /suggest ram upgrade for motherboard D945GTP.

Hi all,

According to cpu-z My present config is as follows.
512 MB Ram in dual channel config.

Memory SPD
-------------------------------------------------------------------------

DIMM # 1
SMBus address 0x50
Memory type DDR2
Module format Regular UDIMM
Manufacturer (ID) Hyundai Electronics (AD00000000000000)
Size 256 MBytes
Max bandwidth PC2-3200 (200 MHz)
Part number HYMP532U64BP6-E3
Number of banks 1
Data width 64 bits
Correction None
Nominal Voltage 1.80 Volts
EPP no
XMP no
JEDEC timings table CL-tRCD-tRP-tRAS-tRC @ frequency
JEDEC #1 3.0-3-3-8-11 @ 200 MHz
JEDEC #2 4.0-3-3-8-11 @ 200 MHz
JEDEC #3 5.0-3-3-8-11 @ 200 MHz

DIMM # 2
SMBus address 0x52
Memory type DDR2
Module format Regular UDIMM
Manufacturer (ID) Hyundai Electronics (AD00000000000000)
Size 256 MBytes
Max bandwidth PC2-3200 (200 MHz)
Part number HYMP532U64BP6-E3
Number of banks 1
Data width 64 bits
Correction None
Nominal Voltage 1.80 Volts
EPP no
XMP no
JEDEC timings table CL-tRCD-tRP-tRAS-tRC @ frequency
JEDEC #1 3.0-3-3-8-11 @ 200 MHz
JEDEC #2 4.0-3-3-8-11 @ 200 MHz
JEDEC #3 5.0-3-3-8-11 @ 200 MHz

The motherboard manual says:
667/533/400 MHZ DDR2 SDRAM.
Four 240 pins ,1.8 v ,SDRAM DIMM with gold-plated contacts
SPD Memory only.
unbuffered ,un-registered single or double -sided DIMMS.
Non-ECC RAM.

Q1. Could you suggest possible ram upgrade up to 2 GB under $ 60.
2. How to identify an SPD RAM module.
3. can singel and double-sided modules mixed used.