Selecting the right Acronis backup software

I have two laptops that need a reliable backup program and I believe Acronis has the program I need. But is it best to order and secure the CD via USPS, or purchase the program and then install online? Unfortunately, I failed to secure the Window Xp OS when this laptop was initially purchased and when I needed a specific OS, securing a file (one) it was a hassle.

And these two laptops have two different caches of memory. One has 60G's, and the other late model has 325G. Do I need to purchase a special program for each system, or can I use one program to backup both. I read that the Acronis Home Plus would be the correct program to purchase as these machines are both used in the home. Have one WD 120G, and one Seagate 500G. Both external HD's.

Can someone help me select the right (appropriate?) Acronis backup program, and the best way to secure a copy?

Thanks

James