Its hard to say. If you pull money out of your current properties to finance a new one you will obviously have less cash flow on your current properties. Then again the cashflow on a larger commercial property may more than make up for that. You will find that in most cases you will need at least 5-10% down on a commercial purchase with 20+% down giving you the best rates. You will have to set up some future cashflow scenarios using estimates of the new payments on your refi’s and on the new property and look at the big picture.
I would stick to 90% on the refi’s if you can…should that be the route you go. You will see much more attractive rates depending on credit. Have you considered selling? I know a few of investors that just sold the residential stuff little by little once they took the step to buying larger complexes.