Hi,
i just saw this post on the web archive and felt I can contribute something here so I finally registered. Maybe this reply will not be correctly recognized to the thread, sorry.
The VPS specs you posted should be more than enough - but the price is too expensive!
I currently run about 20 Tor relays on cheap VPS all around the world: http://globe.rndm.de/#/search/query=torpids
Basically I just care for the bandwidth/included traffic when choosing a VPS. 256MB RAM is enough, disk space doesn't matter at all. Tor doesn't scale that well with CPU cores so 1 core is ok. For only 1 or 2 of my VPS the CPU is the bottleneck (at about 20-30MBit/s), but most are fast enough. Most cheap VPS are based on the OpenVZ virtualization which limits you to their old kernel and sometimes they limit the number of tcp connections (see "cat /proc/user_beancounters"). KVM or Xen virtualisation is better because you have more control on the VM. Most VPS providers add up the incoming and outgoing bandwidth, meaning that you might be able to just send about 500GB with your 1TB plan.
For example with a VPS from www.jiffybox.de for 15€ per month it is possible to push more than 1TB PER DAY(!) (and not per month as with the 18€ plan you mentioned). OVH just released a server for £2,99 per month with unlimited 100MBit/s as well: https://www.ovh.co.uk/dedicated_servers/kimsufi.xml Other typical offers are like 10TB for 10$ or 20MBit/s unlimited for 3€.
Good places to find cheap VPS deals: http://www.lowendbox.com/ and http://lowendtalk.com/categories/offers http://www.wjunction.com/46-vps http://www.webhostingtalk.com/forumdisplay.php?f=104
Best, Torpids