I/O read and Writes
Memory utilization
Physical Disk\Avg. Disk Reads/sec
Physical Disk\Avg. Disk Writes/sec
machine processor time
SQL processor time
Would be a good place to start, Monitor every 5 minutes for a day and see where things settle out on first pass. don't add too much monitoring at once you will not get any numbers that are useful.
Also location probably will not play much into performance unless one site has a much larger bandwidth. The Hard drives personally I would stick with 2 drive's in a raid one config, you can still backup but if one drive fails you're not down and the raid will rebuild the other drive once replaced, Backups are better for corruption than Hardware issues. Make sure your always installing service packs and security patches (Microsoft every 2nd Tuesday of the month)
Oh the other part you can NEVER have too much memory, but the OS has to be able to support it, what OS is the server running/ what are you going to use on the new server?