There are actually sound proofing panels checkout soundproofcow.com they can be quite attractive and easy to install

I am going to up the anti here and suggest Green Glue (in lieu of the foam board) used TOGETHER with ACOUSTIC 5/8" drywall. Green Glue adds 18 dB...and acoustic drywall adds 18 dB. For $5.50/sf, you will have added 36 dB worth of sound proofing in one, single, easy to accomplish installation.

You smear the Green Glue over the drywall panel (2 tubes GG per 1 panel drywall) and then screw the drywall into place. There is no "double install" as you suggested above.

Remember: not all foam board is acoustic. And not all drywall is acoustic. Regular 5/8" drywall = 5 dB. Foam board ranges from 5 dB - 15 dB (super cheap - super expensive). You could be wasting money + wasting money with the products you propose.

Remember: every time you use a metal screw, you LOOSE acoustic insulation. That's why it is important to PURCHASE the Green Glue drywall "caulking" and acoustic "mud" and "tape" system as well. You will need to plug the wholes you create each time you drill into the drywall.

Green Glue = $2/sf; Acoustic Drywall = $3.50/sf. That's where I got my "$5.50/sf" cost from. Installation and accessories are EXTRA.

Have fun.