When we have dedicated servers for each environment like below
Dev. - > Test Server
QA --> Test Server
PROD --> QV Enterprise Server.
In development environment , the source files would be excel, text etc..
In QA Environment ,I hope we would be pushing only the QVW's and not the excel and txt files.If that's the case,how will the QVW will take the path of the excel file or text file? whether we need to have the same structure as in Development environment in QA as well?
That depends on what you want to do in QA. If you want to reload the QVW documents there without changing the scripts then all the sources needed by the QVW documents need to be in the same place as they are on the Dev environment.
"...to repeat the same setup as we have in Dev Environment..correct?"
Not necessarily. What you do in Development may never end up on any of the other platforms. This is your Development environment, meaning that you will experiment, develop, test, try&fail and restart various solutions. Once you start tinkering with or improving your Deployment Framework, you will end up with a development platform that will probably be different from everything else. And that's not bad.
Look at it from the other side. QA shouldn't be a copy of Development. On the contrary, it must be - as much as possible - a copy of your Production environment, so that you can test your new (versions of existing) documentson QA as if you were using them in Production. Only after these tests complete succesfully, you can be 99% sure that pushing these documents to Production won't get you or your end-users in trouble.