I suspect you have a mistake in your question. When you say "OS RAID3" on the "SVR2" specs I suspect you mean "OS RAID5". Personally, I'd caution you that the RAID 5 functionality in Windows isn't up to the level of reliability of a hardware RAID controller. Windows RAID 1 works very well and is "cheap insurance" but I'd recommend spending the little bit of extra money to use a hardware RAID controller if you want RAID 5 and you want it to perform in a solid and reliable fashion.
Running DHCP, DNS, Active Directory, WSUS, and Windows Deployment Services on a box that is handling 30 - 50 client computers isn't any big deal (assuming you install a 64-bit version to take advantage of the 6GB of RAM). The "IIS" and "SQL" roles are really open ended, though, and the chunk of performance they'll consume depends on what you're using them for. I can't figure out waht you mean by "FCS" so I can't comment on that. I assume the disks on "SVR1" are SATA, so don't expect to get any quantity of IOPS out of them. Windows software RAID 1 has worked very well in my experience, but please remember to find any one of the various monitoring scripts out there on the 'net and configure it to run periodically to alert you if a disk fails (since W2K3 doesn't have any built-in functionality to do that).
"FCS" aside, none of the roles you describe for SVR1 are tremendously difficult to migrate to another machine later, so I'm not sure that I see any advantage to using a hypervisor versus running it on the bare metal. Given your low-end disks I'd run it on the bare metal to eek out all the performance I could anyway.
I don't know what your "Access Control Application" is, but Spiceworks is extremely easy to migrate to a different machine later. I'd run Spiceworks and the "Access Control Application" directly on the bare metal on SVR1, too, if I could get away with it. That saves the overhead of a hypervisor on a machine that only has 6GB of RAM and a lot of (albeit mostly small) jobs.
re: SVR2 - Running AD, DNS, and File Server roles on that box aren't a big stretch, though I'd bump the RAM up to 4GB and I'd get a hardware RAID controller.
re: Exchange Server 2003 - I've run Exchange Server 2003 on very low-end hardware for small numbers of users. I've got a production installation now in an office of 17 people running on a box not unlike your "SVR1" machine (similar roles, also a file server, too, running SBS 2003). I think you're pushing it, though, try and host Exchange for 30 - 50 users on either of these boxes. I don't think either box has enough RAM or I/O capacity for an Exchange Server 2003 installation of that size to perform effectively.
As a "cheap fix", I'd replace the "SVR1" machine with a higher-end server-- something with a SAS RAID controller that VMware ESXi supported, 8GB of RAM (or more), at least a single quad-core processor, and a RAID-10 set of 10K SAS disks (or better). I'd run VMware ESXi on the bare metal and the "SVR1" role as a guest instance on that machine. You should still have sufficient I/O capacity left to host Exchange Server 2003 very effectively on that machine. (I did a project in a Customer site with similar needs recently-- migrating SBS 2003 from an old Compaq box to modern hardware-- and we got away with a sub-$3,000.00 Dell PowerEdge R310 to host the replacemnet SBS instance with I/O and RAM to spare for future VMs...)
I'd be curious to hear what you've planned for backup, too.