Are Democrats admitting that lower taxes are good for the economy?

Billary and B Hussein Obama are both saying that the new economic stimulus package will be good for the economy. It is getting money into the hands of people who need it (notice it does not say people who earned it). So aren't they essentially saying that lower taxes are better for the economy? I mean after all, the "rebate" is really the same as paying lower taxes (as long as you are one of the 95% of tax-paying (and a few non-tax paying) Americans that will actually be getting a rebate). So if $150B is good, wouldn't $300B or $500B be even better?