Marty, sharpening should not be necessary when resizing downwards.

1) Down-rezzing is an ersatz method of both sharpening and noise reduction. Just use PS Bi-cubic sharper. Save .JPG at 100%. Lesser quality will destroy the finer attributes of most images, IME.

2) For up-rezzing, I do all editing to the RAW file in ACR, then anything else in PS using a .PSD 16 bit file as the output. I do not sharpen or apply NR at any stage of ACR or PS. I then use Bi-cubic smoother for resizing. I apply any sharpening (USM) or NR necessary to the up-rezzed file. After up-rezzing, I apply any sharpening or NR needed. I do not use any s/w other than Adobe for any of this - no plugins.

Using this method, I can print at A2 on fine art paper from my 5 MPx E-1 without any noticeable artefacts.

Note that none of this will work as advertised if you need to crop severely with a FTs or mFTs camera. It is why I concentrate my efforts on catching images that do not need any cropping to achieve the composition I want.