Help me choose a memory card for my se walkman

i have ordered a new se live with walkman via ebay.
im looking for a 8 gb memory card for the same.

cud u pls suggest which one is the best brand.i found these on the internet

SanDisk MicroSDHC 8GB vs Strontium 8GB MicroSD vs Transcend microSDHC Class 4 8GB | Mobile Accessories

does the memory card performance effect mobile performance??

im going with sandisk 8 gb micro sdhc class 4 card,got an offer in ebay....
thnx