Scalability of Hardware linux and databasea

[bobb10@walla.com (Bob Baker)]

Folks,

I handle tech for small ISP that has < 5000 users.
We are about to do a big marketing push for new users (all those
getting PCs over holidays).

Users will get email and hard disk space. 1GB limit
Wondering if any of you have any metrics on what gets typically used.
Up to now we have never offered more than 10MB and even that never
gets approached (< 1MB on average).

With this bigger limit my boss thinks we might get lots of picture
uploads etc.

With that in mind I'm wondering how much to scale for if we bring in
an extra 10000 accounts.  Est   ?? per user for email. Est ?? for use
per file space.
Any of you been storing pictures from people? Do they do it much? How
much do they store?

Our 2GHz 2GBram linux box has beenhandleing this fine up to now. 

But now I have a budget to upgrade I wondering where I should spend it
(other than storage disks). Any rules of thumb. 2Ghz box handles 5000
light users.

But extra 10K users that are more active or store more may need more
resources in terms of CPU/Memory too. Any thoughts?

Thanks in advance. The info I read here is always a big help to me in
doing my job!

Bob!