Should I file an amended return and 1040X?

I just filed my 2009 Federal income tax return a few weeks ago and sent the I.R.S. a money order for the amount due. Today I received a 1099-SSA form showing that I had received an additional $364.00 (which I forgot to report on line 20a of 1040 form). This is non-taxable Social Security income so I won't owe the I.R.S. any extra money but I was still wondering if I need to file an amended return now or won't it be necessary since the $364.00 is non-taxable anyway?.

Also, does a person open themselves up to additional scrutiny or unwanted attention by filing an amended return/1040X?. In other Words, does this send up a giant "red flag" and cause the I.R.S. to probe, prod and peek into your life -or- do they simply file the new (amended) data and move on?.

I've run a small, home-based business with very low profit margins for years and never had any issues with my taxes (or the I.R.S.) and I've filed every year but I also read that when your self-employed and/or take deductions for home office space, etc the IRS tends to pay more attention to your return and now, if I file an amended return/1040X I'm wondering if it's going to open me up to even more scrutiny or even an audit. Should I just wait for them to sent me a CP2000 since the extra amount won't add to my tax debt anyway?. Must I file a 1040X?. What is the risk/benefit ratio of doing so/not doing so, etc?.

Thanks so much!.