Windows 2003 SBS Premium Capabilities

I support a number of small networks. When I say small networks I mean 5 - 50 PCs. All of which have a single location, at least for now. I have a number of new server installations coming up and I've been considering using a single SBS (Standard or Premium) server for each client.

Mainly because of the flexibility it provides - I can decide to enable/disable Exchange or SQL down the road without incurring a major overhaul.

I guess I'm concerned about the performance, especially clients that will be running an SQL database along with Exchange. I've been reading a lot of posts saying you shouldn't have SQL databse on the DC. Obviously, these are not referring to SBS.

But is there a cutoff? I know M$ claims SBS can handle up to 75 users - hey, just like XP runs on 128MB RAM. Good work boys.

I'm talking about a server w/4GB RAM, RAID 1 for the OS, RAID 5 for the data, redundant powers supplies, same-day warranty. The obvious exception would be a client that needs to be running 24x7 - who doesn't? - and is willing to pay for it (i.e. SAN, multiple servers, etc.)

Am I driving myself nuts? Can SBS 2003 Premium handle the load of 20-30 PCs accessing an SQL database, plus Exchange and company files?

Thanks in advance.