Look at this link:
http://www.irs.ustreas.gov/pub/irs-soi/01in01ts.xls
From the sheet you can see that there were 128,817,051 returns filed for tax year 2001. The top 25% of those taxpayers had an AGI of $56,085 or higher. Now go to the bottom of the table, and note that the same group paid 82.90% of the tax revenue. Note also that this group paid, on average, 18% of AGI in tax. Note that I say on average, because you probably know that the tax code provides for increasing rates as AGI increases.
So my answer is, bring it on! Eliminate progressive tax brackets above the $56k baseline! You lose $151 billion in tax revenue from the people below the line, who don't pay any more federal taxes! You lose another $71 billion by reducing the average rate on the top 25% of filers from 18% to 10%! That's $222 billion you have to make up. That's about 10% of the federal budget. I'll take $50bn from defense if you will take $50bn from entitlement programs, fair?
Now let's look at your supply-side assumption. You have an extra $222 billion that's available for investment and consumption spending. Let's assume that half of that is pure consumption, which yields a net pretax margin of, lets's say, 20%? Assuming you continue the corporate tax at 40%, you just made $9bn back in tax revenue from the effect of additional consumption in that year. Let's assume the other half is invested with a pretax margin of 40%, and you set capital gains taxes at 20%. There's another $9bn. So you make $18bn back the first year in tax revenue, so your annual (additional) deficit drops to $104bn.
What about expansion of the economy and tax base as a result of the reallocation of those dollars to consumption and investment? Do you think that a 5% increase in Gross Domestic Product is reasonable? Can we assume that that increase will be reflected in tax collections? So if tax collections increase by 5% of our now-reduced collection of $1,953 billion, there's $97mm. Dismantle the IRS and you're there.