i use paintshop pro as i dont have photoshop and do my resizing in there with no problems and since i got my new D40x Nikon a few days ago I dont find it sluggish at all I find a top camera and resizing is not an issue
Atrei, you should read this
I follow this procedure when uploading images to Alamy and RB with the exception that when I upload to RB I sharpen the images, wheras Alamy wants non sharpened images.
Remember file size is not as important as the image size. RB has a image size guideline here
I Bicubic upsize a lot of my images in PS taken on my 300D (6 meg) without any visible loss of quality.
I don’t have this problem with my 5D :-)
Obviously if you have heavily cropped a 6meg image, bicubic upsizing to 3900 × 2600 pixels won’t be possible without quality loss.
As James said, use your judgement!