So first off, you aren't able to use Excel on a Chromebook like you normally would on a laptop. There are a couple of workarounds, like:
1. Opening the spreadsheet with the MS Excel Online App
2. Using the Office Editing Chrome extension
3. Using Google Docs
With that out of the way, the Toshiba Chromebook 2 and Acer C13 come highly recommended, so you should check those out. I have the Chromebook 2 and am pretty happy with it.