I signed up when the halloween special was going on, and have been very pleased with the services provided. My server has been up since the day after they gave it to me, I have cpanel for $19.00 extra and put 11 clients on it already with no issue. I would recommend.
30 - 40 reseller accounts with how many accounts per reseller? 5 = 200 sites on the server - 256MB ram and what processor? Definately upgrade. I would put 1gb + for 150 websites and depending on whether they use alot of scripts or they are just static sites you may need a processor upgrade.