(Image credit: Getty Images) A mega backdoor Roth IRA is one of the most powerful strategies available to high-income earners who want to maximize tax-advantaged retirement savings. The name "mega backdoor Roth" sounds big and exciting, and it is. It is a way to get money into a Roth account, where it can grow tax-free and be withdrawn tax-free in retirement, once certain conditions are met. To fully understand how a mega backdoor Roth IRA works, it helps to first look at its predecessor — the standard backdoor Roth IRA — and then explore how this enhanced version expands your retirement investment options. From just $107.88 $24.99 for Kiplinger Personal Finance Become a smarter, better informed investor. Subscribe from just $107.88 $24.99, plus get up to 4 Special Issues CLICK FOR FREE ISSUE Sign up for Kiplinger’s Free Newsletters Profit and prosper with the best of expert advice on investing, taxes, retirement, personal finance and more - straight to your e-mail.…