Shopping for a 4GB SD card, so many different types?

Hi everyone, I bought a Samsung I730 PDA phone off of Ebay:




I am looking for a 4GB Secure Digital card for it and am wondering what I should get because there are so many different types. It appears there are a few 4GB SD cards that are not SDHC, but the majority of them are. What is the difference between a class 6 SDHC card and a class 4? Apparently class 4 has better compatibility with non SDHC devices or something?


Also too, transfer speeds are pretty important to me so I am wondering if any of those 22.5MBps (150X) cards will be compatible.

Thanks again.

I found this one on newegg, what do you guys think of this, is this a good card?

http://www.newegg.com/Product/Product.aspx?Item=N82E16820163159