There is less need for high psi than you are led to believe, when I had 400 psi available, I rarely needed it with 200psi being adequate for almost everything...............even when faced with Black Top, or heavily soiled Chinese / Indian resturants, etc, it's the chemical and aggitation that does the work.
You could clean effectively, with as little as 70 psi, provided that you have suitable chemicals, allow sufficient dwell time, aggitate adequately and use good wand technique.
Some will say this is rubbish and they will get a far better result, with their 1000 psi T/M, but, they won't be using the massive power available, in domestic, or even in most commercial work.
A T/M will, in most cases, be quicker and it's handy, occasionally, to have the extra power available, but the addition of an INLINE heater and some form of mechanical aggitation will get you much better results than your current set up.
A fair number of people use the little Sebo, but, it's very light and there are other options worth looking at.
rob