Those use no system resources but can use a lot of bandwidth. I'd suggest finding a provider who allows IRC. Just make sure you get whatever their lowest end hardware because you need know more than .1% of the CPU. RAM is nothing..
As Raine said..they would use very little system resources and a fair ammount of bandwidth. Don't think you would need a very high end dedicated server. Try e-mailing [email protected] with a custom quote on a low end server or consider using shells.