It's difficult to give useful advice when you've provided very little info, my guess is that that's why you haven't got the answers you hoped for.
Yes, you can adjust the power - but can you adjust it enough? The power can be reduced steplessly to 1/32nd of maximum, but as others have said that may not be enough to allow you to use the 500's in a small space, let alone the 750's. You'd probably be better with 250's max.
Conversely, the 750's may not produce enough power in a large space!
So, my suggestion is that you get the 250's for your home use, and the add a 1000 (or more) if you find that you need it later.