Upgrading to Air, is the processor fast enough ?

I realize this may come off as a stupid question, but my knowledge about processors is nt adequre to understand the differences. So I have a Macbook 2008. It has Processor 2.4 GHz Intel Core 2 Duo Memory 2 GB 667 MHz DDR2 SDRAM. I want to upgrade to a MBA 1.8GHz dual-core Intel Core i5 processor with 8 GB of RAM. So the processor speed goes down, but it is a new Ivy Bridge processor. How can I make this comparable. Will it still be a significant speed pump ? Any help would be great. Oh and I realize that the RAM bump will make multitasking much faster, my concern lies in the processor.

Thanks in advance.