I was interested in getting a TI-99/4A system for a while, but after I
finally got a couple of systems with PEB (Periperal Exansion Box)
floppy drive setups I never got excited enough to do anything with
them and moved them along to other collectors.
If you ever do get a floppy drive setup you might want to take a look at this:
ftp://ftp.whtech.com/pc%20utilities/TI99-PC_3.0.0.zip
I never got around to trying it myself. It looks like it could be used
to write TI-99/4A floppy disks directly from a PC and there is a large
collection of archived floppy disk images on that site.
-Glen