The large servers are usually not an issue because you can setup the full backups on the weekends and the incrementals during the day or night (one time or multiple). A network share works best, make sure you have a gigabit network card in each server and you can usually get 1.5-2 gigabytes of compressed data (if you're using compression) through the pipe since you're splitting the read and write on the source and destination.
Make sure you stagger the backups so that your destination doesn't become taxed from imaging from multiple machines at the same time. I normally setup a server with SATA drives or SATA NAS and a tape backup on it. Since the images are constantly changing and writing to them is only done on a regular basis SATA works fine, but I backup the images to tape as well just inc case of full DR requirements.
If you are getting a NAS I would pick one with Microsoft storage server OS, some linux based NAS units that present NTFS partitions do not work with BESR because it is looking for native ntfs share.
It is still a lot easier to restore an image flat file and then restore a full server than using tape directly.
If you have any other questions let me know. You can also do a nice test of your servers by setting up a VMWare ESXi server (free) on a decent size box and vmware convert the images directly to virtual machines.