Best spreadsheet excel app?

[roccobladr]

I'm looking for an app on my iPad the would be able to do the following:

Open up an .xls file from email
Be able to edit xls file from open office (Mac version)
Send xls file as an email attachment.

I don't need any crazy features just basic calculations like addition. Dropbox features would be nice but not mandatory. I've looked into Numbers but I don't really need all of the features and would rather not spend that much money if possible and I use open office on my MacBook Air so it needs to be compatible.

Any thoughts?