Q: How do I store an Excel document on my Mac on my iCloud site?

Ok. After reading a number of answers to questions similiar to my mine, here is what I have gleaned from thse answers:

1) I think that I cannot store MS Office Docs on iCloud unless I purchase iWork and store that App in iCloud.

2) Then, I can drag Excel (.xlsx) documents from my Mac (running Mountain Lion) onto the Numbers App and store the workbook as an Excel document in Numbers.

3) If I want to download the document, I sign on to iCloud and drag the Excel file back to my Mac (or other properly setup device).

Is this correct?

It seems as if the design of iCloud is setup to use iWork as the main engine of document storage. So, it is not like Dropbox which allows storage of any legit file type without the need for a specialized App.

iCloud also allows access to these documents by other devices (iPads, iPhones, Windows PCs and otherrs) as long as they are properly setup to access iCloud (similiar to Dropbox) and have the iWork App to display or alter the document (unlike Dropbox).

Is this correct?

Thanks.