On my 1040 last year, my adjusted gross income was $127,594, my total tax was 21,075 (16.5% effective tax rate); your presumed tax on 100K (25%) was off by a deceptively huge amount (gee, who would have guessed). Even the deceptively quoted 23% FairTax sales tax rate is considerably above the typical effective income tax rate for a middle class single guy.
Then use your "effective" tax rate and do the calculations. The FairTax calculator has been available on this thread for you to work with. Try it.
You might do even better with a closer analysis and remember that hasn't counted your purchases under the income tax which will cost you another 9% (in hidden taxes which are there whether you wish to beliefe it or not)... that would actually make you a few percent better off under the FairTax. So if your figures are reasonably close (and remember your savings and income from it or any capital gains are not taxed under the FairTax) you wouldn't do badly at all under the FairTax.
Use the Calculator and figure it out for yourself.