Don't listen to any of the above fools :P (love yas really), you could happily support 300 players with some of their wild suggestions.
A £30 machine off eBay will run a server better than fine... for around 40 players (assuming 512kb/s upload). Specwise for 1.9, your going to need around 500MHz or above, largely depending on the amont of NPC's and mobs.
If you require a lot of maps, then your going to need a lot of RAM. 512mb is the generally accepted minimum for 1.4, but this will obviously depend on the amount of maps you have. 128mb is fine for a streamlined design with only the minimum maps needed (running Win98 or TinyXP).
As for upload speed, they're all crazy again. Work out how many players you want to support and pay for upload accordingly. If you only plan for 20-30 players at peak times, your only going to need a 256kb/s upload (variable depending on the amount of mobs on screen per player).
It annoys me when people post crazy specs for playercounts that are unlikely to reach 30. You need to quantify specs by players... not just get anything.
/Leo