GarryN
before spending out you can try some new methods,
for example do you prespray? this can have a massive advantage when using cheap end machines. I would test micro splitters, and some of the best detergent pre sprays with yes with your rug doctor.
you can combine different systems. for example rotary machines can be used before and after with something like chary pads. if you scrub, rug doctor and pad after you might see different results. rotary is THE most productive in terms of sq ft per hr
Just think of the extraction part as the rinse part of any method. only needed on really dirty carpets. get a great vac and your get on top on this as well. time spent on this part saves loads of time on the later parts.( before rinse) many here will tell you that some clients think you have wet cleaned a carpet when all you have done is given a proper vac. ( up to 15 mins a room average) do this add in a good pre spray and extraction can take a fraction of the vac time. line up each part of a method and you become more effective. pre spray needs dwell time.
You can go the shampoo rotary road.
best book a prochem course as they teach preventive, corrective, and salvage methods. plus you will get a greater understanding for their product range. easiest to understand. many would have you believe the machine is the most important part, its just that part of any method. it will not matter how expensive the extraction machine is because if the dirt is not emulsified it ant coming out how ever many passes you make.
I am sure that if you run a company you get others to do the work, well investing large sums of money into equipment that can be damaged if miss used is not something you want to do. rotary, and cheap extraction is the way forwards. hundreds of thousand of yards of carpet is cleaned each year by contractors with rotary and basic equipment. and these are massive companies working for FTSE clients. winter can be an issue.
regards heat if you have good emulsification with heavy scrubbing you can reduce the amount of heat needed. you only need bucket heaters.
with the type of work you doing its the end result that counts and not impressing any clients with how great your machine looks.
you can find some really great pad methods. they dont get talked about that much but they work great.
also an ozone gen would work great for you at removing odours from houses.
hope this helps, respects