Any of these will do but Class 2 is pretty old standard now and class 10 is the best
http://samsunggeeks.com/2012/05/20/micro-sd-cards-smartphones-speed-class-explained/#.UihTlj9V_4M
Try picking something in the middle
You don't mention what version of Excel you are using but try these links:
http://www.mrexcel.com/articles/due-dates-with-conditional-formatting.php
http://blogs.office.com/b/microsoft-excel/archive/2013/04/04/mvp-tutorial-using-conditional-formatting-to-highlight-dates-in-excel.aspx
Personally I use the RAZER Carcharias and am very happy
http://www.newegg.com/Product/Product.aspx?Item=N82E16826153043
The headset covers your ears and is very comfortable even when gaming for hours :-)