Remote backup

I’m setting up an off site backup system where my primary office & remote office send each other backups over the internet each night via FTP. My original plan was to purchase 2 basic PCs and then install a 500GB HDD in each PC with serv-u ftp server on them. The “sending” office would use SyncBackSE to send its backup to the PC at the other office where serv-u server is running.
I decided to try and find a more all in one solution. I’ve looked at and purchased a Hammer-Storage N1200 myshare device, but the FTP server on it is very flakey. I was going to try a LaCie Ethernet Big Disk instead but I’ve read a couple reviews saying the FTP server on it was also suspect. I’m willing to spend anywhere upto $600 (each office, $1200 total) for a good solution. Does anyone have any recommendations? FYI – My backups will be around 100GB and I’m hoping to use SyncBackSE on the send (or source) side.