Hello,
Is it a good idea to host phpbb forum with 4 -5 000 dayly vistors on a hsared hosting here?
Thanks,
ivanrk
You could, but as always make sure it is up to date 
Thank you Stephen!
Actualy they have only 1500 visitors/day but there are moments when the forum is empty and moments when there are 200 online users in the same time and i am not sure how much CPU power will be necessary - I will move heir site here.
200 simultaneous users can be resource intensive, atleast in case of vBulletin. But it also depends on what is the percentage of active users among these logged on users. If they are going to constantly see this big number of simultaneous users(now or in future), VPS may be the way to go for them.