Not too familiar with dtsx packages - can they be created/run outisde Visual Studio?
Is BIDS (Business Intelligence Development Studio) just required to do all the above (in Visual Studio) or is it an independent development enviroment for dtsx packages?
Please shed some light if you can (and get some eazy rep)!
Absolutely! Just double click on it (launches dtexecui.exe) or use the dtexec command. See how all the ways stack up here.
Answering some of the other questions:
BIDS is the sole environment to build SSIS packages. You could handwrite the XML, but good luck to you on that one. BIDS is a standalone product as well as an integrated one, so just install it off of the SQL Server DVD. You will not have to buy Visual Studio in order to use BIDS.
Visual Studio is based on sets of functionality in Visual Studio "packages" (vspackages). BIDS is just Visual Studio with the vspackages for SSIS, SSRS, and SSAS development. Those same vspackages can be used through "normal" Visual Studio if you already have that installed.
If you don't have Visual Studio installed, then installing BIDS installs it.
Although you can run SSIS packages outside of VS, there's little you can do to debug them that way. It is not practical to create them outside of VS.
Is there a reason you want to do this?
Yes, you can get rid of VS2005 as far as BIDS is concerned. Install Visual Studio 2008 SP1, then install the SQL Server 2008 bits you need, including BIDS 2008.
If you still need to work with SQL Server 2005 SSIS packages, then you still need VS2005 to work with them.