Nextline
I am exactly the same as you, always used prochem, got a good discount but there are some good chemicals to add to the kit box.
1, Alltec citrus prespray - pretty universal stuff and works v. well
2, Solutions no 2. - Used as a prespray, needs plenty of agitation (ideally mechanically) but no need for a extraction liquid in the tank, just some deodoriser & water. This works on the microsplitting principle (do a search on microsplitting to learn more via the threads). Advantage of this is you can use it on carpets & upholstery, but because it is not detergent based you find the fabric/carpet will not resoil as quickly.
I am still unsure which manufacturer/process to go down fully so I just pick and chose
Happy with prochem machines though, easy to maintain yourself & pretty reliable (in my view)
Regards
Tim